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Cataract Surgery

In a nutshell

This page discusses surgery for the treatment of cataract. Cataract is a clouding of the lens of the eye which can cause visual impairment and blindness. Cataract surgery involves removal of the eye's natural lens, followed by implantation of an artificial intraocular lens. Cataract cannot recur in an eye with an artificial lens.

Well-performed cataract surgery can be effective at improving patients' vision (including reversing blindness) and quality of life. While surgical quality varies in practice, we have seen examples in the literature of high rates of surgical success. Based on one long-term follow-up study of cataract patients in three developing countries, patients' self-reported quality of life after surgery was similar to that of matched controls without visual impairment.

Our rough estimate of the cost-effectiveness of cataract surgery suggests that it may be competitive with our priority programs; however, we retain a high degree of uncertainty. In particular, we are uncertain about the total costs of providing a patient with access to cataract surgery, the proportion of surgical patients who have severe visual impairment or blindness, and the rates of surgical success in programs supported by charities.

We have conducted some preliminary conversations with organizations that fund cataract surgical programs. We have not evaluated the track record of programs to increase access to cataract surgery. Should we decide to prioritize cataract surgery for further research, we believe that the most promising next steps involve learning more about specific programs to increase access to cataract surgery.


Published: August 2016

What is the problem?

What are cataracts?

A cataract is a clouding of the lens of the eye which prevents clear vision. Most cases of cataract are related to the aging process, as proteins in the lens degrade, but occasionally cataracts are congenital or develop after eye injuries, inflammation, or other eye diseases.1 Cataracts can develop in one or both eyes. Our understanding is that there is no proven preventative or medical therapy for cataract.2 Throughout, we use the term 'operable cataract' to refer to cataracts which have progressed to the point where surgical intervention is advisable, and for which there are not contraindications rendering surgery inadvisable.

How severe is the problem?

Cataract is the cause of a significant proportion of blindness and visual impairment, causing blindness in approximately 20 million people (more). We have not investigated the variation in and progression of visual acuity loss due to cataract in detail. Because visual impairment due to cataract may be mild at onset, in this report we focus on the severity of visual impairment in persons who seek out or are referred to cataract surgery.

We have not focused on attempting to quantify the effect of blindness on quality of life for people with cataract in developing countries. We have reviewed some evidence that persons visually impaired from cataract report lower quality of life than similar persons without visual impairment (more), and we note that the Global Burden of Disease (GBD) study (2010) assigns severe visual impairment or blindness a disability weight of 0.2 (more).

Cataract prevalence

We have not investigated cataract prevalence in detail. We believe, as is widely cited, that cataract is a significant cause of blindness and low vision. In 2010, the World Health Organization estimated that cataracts are responsible for approximately 50% of world blindness, and that approximately 20 million people have blindness due to cataract.3 The burden of blindness due to cataract falls disproportionately in the developing world, where people are less likely to have access to surgical care to prevent progression of cataract to blindness (more).4 Studies of all-cause visual impairment estimate that 90% of people with visual impairment or blindness live in low- and middle-income countries5 and that the prevalence of cataract among people with blindness varies but is more than 55% in some countries.6

Effect of cataract on visual acuity

In this section we discuss the measurement of visual acuity and the evidence for the impact of cataract on visual acuity. We have not seen high quality evidence about the distribution of severity of visual impairment (e.g. the proportion of blindness) among persons with operable cataract. We have not investigated the rate of progression of cataract.

How is visual acuity measured?

It is our general understanding from the literature7 that the severity of visual impairment due to cataract is typically measured using an eye chart (for example, a Snellen chart or LogMAR chart). The patient under evaluation stands a fixed distance from the chart and is asked to read the smallest row of letters which can be made out. In contexts with high prevalence of illiteracy, it is common to use the E chart; patients are asked to show (e.g. with three outstretched fingers) the orientation of letters 'E' arranged in rows like those of a Snellen chart. Visual acuity may be measured as uncorrected visual acuity (UCVA; no eyeglass correction), presenting visual acuity (eyeglass correction if the patient presents for the exam with eyeglasses and not otherwise), or best-corrected visual acuity (BCVA; eyeglass correction is provided for the examination). UCVA and BCVA generally differ for patients who have received cataract surgery because the intraocular lens (IOL) used in the surgery reproduces all functions of the natural lens with the exception of accommodation, or the ability of the eye to focus on both distant and near objects. The standard (monofocal) IOLs used in cataract surgery only allow distant objects to be seen clearly; hence patients are likely to require spectacles for near vision.8

Visual acuity is reported as the ratio of the distance at which the patient can distinguish a fixed detail (e.g. a letter) to the distance at which a person with 'normal' vision can distinguish the same detail. In the metric system, visual acuity is reported relative to 'normal' vision of 6/6;9 in the imperial/US customary system of measurement, visual acuity is reported relative to 20/20 'normal' vision. For exam patients unable to make out the largest letter on an eye chart, reading distance is reduced until the patient can distinguish it, at which point letter size and distance are noted. Visual acuity in patients unable to distinguish chart letters at any distance is often reported as CF (ability to count fingers at a given distance; for example, CF 1 meter indicates the ability to count the examiner's fingers at one meter), or HM (ability to detect hand motions at a given distance), or LP/NLP (ability or inability to detect any light; e.g. a penlight shone into the patient's pupils).10

In this review, we focus on bilateral (binocular) visual acuity, which is measured with both eyes open.11 For example, if a person has cataract in one eye but no visual impairment in the other eye, they are likely to experience little or no impairment in bilateral visual acuity. We focus on bilateral visual acuity because we find it plausible that bilateral visual acuity or visual acuity in the best eye correlates better with quality of life than does visual acuity in the operated eye (which may be the worse-seeing eye and hence have little effect on overall visual acuity of the patient). We have not closely investigated this assumption.

In the United States, blindness is legally defined as best-corrected visual acuity equal to or worse than 20/200 (equivalent to 6/60 in metric units).12 The World Health Organization's classification of diseases defines binocular blindness as presenting visual acuity of worse than 3/60 in both eyes. Binocular severe visual impairment is defined as visual acuity worse than 6/60 (but equal to or better than 3/60). Visual acuity of less than 6/18 but equal to or better than 6/60 is classified as "moderate visual impairment", and visual acuity of ≥6/18 is considered "mild or no visual impairment".13 Because of the WHO recommendation that after cataract surgery, 80% of eyes have presenting visual acuity better than 6/18, and fewer than 5% be worse than 6/60,14 good visual outcome in studies is often measured and defined as 6/18 in the operative eye.

What is the preoperative visual acuity of cataract surgical patients?

Benefits of cataract surgery include reversal of existing blindness or severe visual impairment, and/or prevention of future blindness or severe visual impairment. In this section we discuss the preoperative visual acuity of people who receive cataract surgery (i.e. what portion of cataract surgery patients have blindness or severe visual impairment), in order to inform our estimate (below) of the proportion of cataract surgeries which reverse blindness or severe visual impairment. We have found limited evidence about cataract surgery patients' preoperative visual acuity, and are highly uncertain about the proportion of patients who have blindness or severe visual impairment. Credible estimates that we have seen range from as high as 47% to as low as 10%. At this stage, because we find this limited evidence sufficient to inform our rough cost-effectiveness analysis, and because we expect that we would learn more about the preoperative visual acuity of patients served through further investigation of particular organizations, we have not prioritized further investigation of this topic.

Our current best estimate of the proportion of cataract patients who have blindness or severe visual impairment is based on findings from a research network of ophthalmologists whose members were asked to collect information about the cataract surgery case mix in their hospitals.15 This study reported preoperative visual acuity data16 by WHO region and by countries' Human Development Index (HDI).17 For patients in countries with HDI <0.5 (all in the WHO Africa region), 47% had reported visual acuity <6/60. (As discussed above, if measured with presenting correction, this is the WHO threshold for severe visual impairment.) Overall, in the WHO African Region, 39% of patients had reported preoperative visual acuity <6/60. In countries with 0.5≤HDI≤ 0.6 (all regions), 32% of patients had preoperative visual acuity <6/60 (ranging from 24% in the WHO Eastern Mediterranean region to 42% in the WHO Western Pacific region).18 Because this data was collected nonrandomly through opt-in self-reporting without supervision or verification, we have low confidence that it is representative of all cataract surgical patients. We are uncertain about the geographic representativeness of responses from hospitals in developing countries;19 in total, data from 1272 patients were recorded from countries categorized as low Human Development Index (HDI) (<0.5), and 5490 from middle-low HDI (≥0.5 but ≤0.6).20 We are uncertain whether the collected visual acuity data was standardized as uncorrected, with presenting correction, or best-corrected.21 If this data includes measurements of visual acuity with best correction, it likely underestimates the level of visual impairment experienced by cataract patients; to the extent that it includes measurements of uncorrected visual acuity in persons with access to correction, it likely overestimates the level of visual impairment experienced.

In conversation with us, CBM (formerly Christian Blind Mission), an organization whose activities include support for cataract programs, estimated based on surveys of partner organizations that only 10-30% of the cataract surgical population served have blindness or severe visual impairment, because people with less severe visual impairment are better able to access services.22 We have not reviewed the methodology or results of these surveys.

We have seen a small number of studies which report the proportion of patients who have preoperative visual acuity of <6/60 with no or presenting correction, summarized in this footnote.23 (We have also seen studies of cataract surgical outcome which do not report preoperative visual acuity, or report it with correction or by eye.) Because we are uncertain about how representative such studies are of the population served by charities' cataract programs, because we believe our current estimate of preoperative blindness is sufficient for the purposes of our rough cost-effectiveness estimate, and because we expect to learn more about preoperative visual acuity if we engage with charities that support cataract programs, we have not conducted a thorough or systematic search for such studies.

What is the rate of visual degeneration due to cataract?

In addition to reversing existing blindness and severe visual impairment, cataract surgery may prevent future blindness or severe visual impairment due to cataract. However, we are highly uncertain about how rapidly or reliably cataract causes degradation of visual acuity to blindness. (In other words, how likely is it that a patient who receives cataract surgery would otherwise have severe visual impairment or blindness in a year, or in five years, or before death? What yearly decline in visual acuity would the average cataract surgical patient experience if they did not receive surgery?) Hence, at this time we have not included benefits from prevention of future blindness or severe visual impairment in our rough cost-effectiveness analysis. Better understanding the progression of cataract is one of our potential topics for further investigation.

Effect of cataract on quality of life

We make the intuitive assumption that persons in developing contexts with severe visual impairment or blindness due to untreated cataract have notably lower quality of life than they could if their cataract were successfully treated. We have not closely examined evidence quantifying the effect of visual impairment on quality of life. In our rough cost-effectiveness analysis of cataract surgery, we estimate a cost per blindness or severe visual impairment reversed, as opposed to quantifying the impact in terms of disability-adjusted life years (DALYs) or other cross-comparative metric. At this stage we have not attempted to directly compare the cost-effectiveness of cataract surgery to that of our current recommendations. This may be an area for further work.

We have not done a thorough literature review on the effect of cataract on quality of life, but our impression is that quantitative evidence is sparse.24 The Cataract Impact Study25 is the only study of which we are aware on the long-term impact of cataract surgery in developing contexts. In this study, 43-51% of patients had preoperative visual acuity <6/60 with available (presenting) correction.26 At preoperative baseline in each country, vision-related quality of life (VRQoL) scores27 showed that people with untreated cataract who later accepted surgery had significantly worse scores in all three VRQoL categories (general functioning, psychosocial, and overall eyesight) compared to controls with normal vision.28 Reported health-related quality of life (HRQoL) scores29 at preoperative baseline among persons with cataract who accepted surgery were also significantly lower than those of the control group in all five EQ-5D categories, with the exception of pain/discomfort in patients in Bangladesh.30 We are not confident in the quality of evidence provided by such self-reported quality of life metrics. It is also worth noting that these metrics include only participants at baseline who accepted the offer of surgery, and exclude identified cases who refused surgery.31

Disability weight of visual impairment

We have previously written about DALYs and disability weighting here. The Global Burden of Disease (GBD) study (2010) estimates the disability weight of severe visual impairment at 0.191, and 0.195 for distance vision blindness. Disability weight of moderate distance vision impairment is comparably very small at 0.033.32 According to these disability weights, correcting blindness or severe visual impairment to moderate impairment saves 0.16 DALYs per year. This study suggests caution in the interpretation of the disability weight of blindness: in GBD 2004, it was estimated at 0.60.33 We have not investigated the methodology of this study in detail, and we have not attempted to interpret the strength of evidence provided by this metric. Note that DALYs in this study are not discounted for the fact that they occur predominantly at the end of a life.

What are the barriers to accessing cataract surgery?

In conversations with organizations that research or implement cataract-related interventions, and/or via a 2016 literature review of barriers to cataract surgery in Africa,34 we have seen the following factors identified as affecting access to cataract surgery. In no particular order:

  • Lack of awareness that the condition is treatable.35
  • Lack of access to cataract surgical services.36
  • Distance, transportation, and food at the hospital.37
  • Mobility, age, and reliance on family.38
  • Cost.39
  • Fear.40
  • Reputation of the eye care institution: the institution's relationship to the community, trust in the institution, and perception that patients will receive good quality, respectful eye care at a fair price (as opposed to fear due to prior community experience of poor visual outcome of surgery).41
  • Prior contact with the eye care institution or advance information so that patients come mentally and physically prepared for surgery, as well as individual counseling.42
  • Low demand for surgery even among patients who are informed about it and can access it at no cost.43

We have heard differing opinions on the extent to which supply-side barriers such as workforce availability, training, infrastructure, and consumables are major barriers to improving access to cataract surgery.44

What is the program?

Cataract surgery

Cataract surgery involves the removal of the eye's natural lens, followed by replacement with an artificial intraocular lens (IOL). There are three major approaches to cataract surgery.45 In our review of the evidence of effectiveness of cataract surgery, we have predominantly focused on manual small incision cataract surgery (MSICS), because it is our understanding that this procedure is common in developing contexts,46 and that it is comparably effective47 to higher-cost48 phacoemulsification, the standard method in developed contexts.49

Pre-surgical screening prior to recommendation of cataract surgery attempts to identify causes of visual impairment, including comorbidities. Whether a cataract is considered operable depends on assessment of how much visual acuity the patient is expected to gain from surgery. However, in some cases comorbidities are not discovered until after the surgery has been begun, which may lead to poor outcomes.50

Improving access to cataract surgery

Our understanding of programs which aim to improve access to cataract surgery is based on five conversations with charities and experts in early 2016.51 It is our preliminary understanding that interventions to improve access to cataract surgery have a limited track record;52 the International Center for Eye Health (ICEH) told us that it previously conducted a literature review to identify interventions specifically designed to improve access to cataract surgery, but found none;53 we have not examined this review.

Our conversations identified the following broad approaches to directly improving access to cataract surgery:

  • Identifying people in villages who need cataract surgery and connecting them to services; this may involve paying transportation costs.54 One approach to this involves the Portable Eye Examination Kit (Peek), a mobile app designed to measure vision and use GPS to identify concentrations of surgical need.55
  • Building surgical capacity and quality at existing hospitals (for example, training staff, providing equipment and consumables, strengthening referral networks).56 In particular, the Seva Foundation supports collaboration between its partners, and its Global Sight Initiative creates a mentor-mentee relationship between hospitals.57
  • Sending a visiting eye care team to a local hospital as a temporary supplement to surgical capacity.58
  • Establishing cost subsidies for cataract surgery, either directly or via a model in which income generated from wealthier, paying patients subsidizes free services for patients unable to pay.59
  • Improving surgical quality through monitoring.60
  • Partnering with communities to build new hospitals.61
  • Program design and development.62
  • Local political advocacy.63
  • Community education and awareness-building, including by training local counselors.64

Does the program work?

We believe evidence shows that well-performed cataract surgery can reverse blindness and severe visual impairment and restore significant quality of life. We have seen some evidence that cataract surgery can be effective at reversing blindness and severe visual impairment with low incidence of long-term surgical complications, although we have also seen significant examples of poor visual outcomes. We have seen some evidence that cataract surgery is effective at restoring quality of life to levels matching peers without cataract. We have done limited investigation at this stage into whether programs to improve access to cataract surgery are effective.

Do surgeries improve visual acuity?

We have not completed a comprehensive review of the evidence of the effect of cataract surgery on visual outcomes. Based on preliminary investigation which identified a small number of studies, we believe it is possible for cataract surgery to achieve good visual outcomes with low rates of complications. However, some evaluations of field work show high rates of poor visual outcome after surgery. In our rough cost-effectiveness analysis below, we (fairly arbitrarily) estimate the effectiveness of surgery at 80-95%. We expect that in the course of evaluating cataract surgery programs for potential recommendation, we would learn more about the visual outcomes of surgeries supported by the program. Hence, beyond establishing that cataract surgery is potentially highly effective at reversing blindness or severe visual impairment, we have not prioritized a thorough review of rates of surgical success.

Our review of the literature on cataract surgical outcomes has focused on identifying studies of manual small incision cataract surgery (MSICS) which report both preoperative and postoperative visual acuity (uncorrected or with presenting correction), by patient (as opposed to by eye), using the visual acuity threshold of 6/60. We have not found studies which directly report per-patient or per-eye change in visual acuity. Based on three studies identified (see table), we believe that success rate in converting a patient with visual acuity <6/60 to visual acuity ≥6/60 may be as high as 95%.65 Because this estimate is based on a small number of studies, all of which took place in large eye care centers in India in 2003-2005, we have low confidence in its accuracy and representativeness. However, we believe that these studies demonstrate that high-quality cataract surgery can have very high rates of reversing blindness and severe visual impairment.

Study Patients with VA<6/60 preop Patients with VA<6/60 post-op Context
Venkatesh et al. 2005 (a) 88.5%66 5.3% at 40 days, 12% of patients lost to follow-up.67 Review of records at Aravind Eye Hospital (India) for 593 patients on six randomly selected days, measuring outcomes of three high-volume surgeons.68
Venkatesh et al. 2005 (b) 100%69 1% at 40 days, no loss to follow-up.70 Prospective study of 100 consecutive MSICS patients with white cataract at Aravind Eye Hospital, India.71
Gogate et al. 2003 85.8% (BCVA, no preoperative UCVA data presented)72 4.3% at 6 weeks, 3.9% of patients lost to follow-up.73 Randomized controlled trial (RCT) comparing outcomes of MSICS and ECCE at Poona Blind Men's Associations HV Desai Eye Hospital (HVDEH) in Pune, India.74

Note that the threshold of postoperative visual acuity ≥6/60 is a much lower threshold of success than the common threshold of 6/18 for 'good' surgical outcome.75 However, we have selected 6/60 as our threshold of interest based on the notion of reversing a blindness or severe visual impairment, and based on the comparative GBD disability weights of severe visual impairment and moderate visual impairment. We find it plausible that quality of life (our true metric of interest) declines smoothly with declining visual acuity (in fact, conversation with an author of the Cataract Impact Study suggests that the decline is linear),76 hence we are aware that any threshold metric of visual acuity is fairly arbitrary. At this stage of our investigation, we consider this threshold metric to provide us a reasonable rough estimate of how often (though not how much) cataract surgery improves the visual acuity of a patient with severe visual impairment or blindness. We discuss the magnitude of impact of cataract surgery on quality of life below.

Further examination of evidence about the effectiveness of cataract surgery reported by eye could influence our view on the effectiveness of cataract surgery, however we have not yet reviewed studies reporting that metric.

Examples of poor surgical outcome. We have encountered studies of cataract surgery which demonstrated high rates of poor surgical outcome. The 2001-2003 Pakistan National Blindness Survey77 found that almost a third of cataract surgeries had resulted in presenting visual acuity of <6/60.78 Patients in this national survey received cataract surgery from a variety of sources which may not be representative of opportunities that we would potentially recommend. However, in a 2006-2007 prospective review of outcomes of Sightsavers-supported ECCE cataract surgery in patients with VA<3/60 in Kaduna, Nigeria,79 (which may be more representative of cataract surgery programs that we could recommend) nearly 10% of patients had visual acuity <6/60 at 8-week follow-up.80 In the Cataract Impact Study (introduced above), postoperative visual acuity outcomes were poor (<6/60) in 6%, 15%, and 19% of patients in Bangladesh, the Philippines, and Kenya respectively.81

Surgical setting. Researchers we spoke with from the London School of Hygiene and Tropical Medicine (LSHTM) expressed that evidence has shown that cataract surgery performed in the field (buildings temporarily converted into operating facilities) yields poorer results than cataract surgery performed in a hospital setting.82 Additionally, CBM staff told us that while CBM used to support surgical eye camp work, almost all CBM-supported surgeries now take place in a hospital setting.83 Sightsavers mentioned that ensuring surgical quality was more difficult when surgeries were delivered in a camp setting.84

Measuring surgical success. In developing contexts, low rates of follow-up may make assessment of postoperative visual acuity challenging. A 2013 observational study in 40 eye care centers in 10 countries of Asia, Africa, and Latin America found high correlation at the facility level between visual outcome as measured in patients less than three days postoperatively, and visual outcome measured 40 days or more postoperatively, suggesting that visual assessment at discharge without follow-up may be a sufficiently informative metric of visual outcome of cataract surgery. The study also found that visual outcome in patients who returned for follow-up without additional prompting (about half of patients) was highly correlated with visual outcome in all patients for whom follow-up data was recorded (93% of patients), suggesting that assessment of only those patients who return for follow-up unprompted could likewise be a sufficiently informative metric.85 We have not examined this study in detail.

Do surgeries improve economic outcomes?

We have not reviewed the evidence for economic benefits of cataract surgery. This may be a topic for our potential further investigation. In conversation, we have briefly discussed positive economic effects observed in the Cataract Impact Study.86 Although we have not conducted a search for evidence about economic effects of cataract surgery, we are aware that Essue et al. 2014 (the VISIONARY study) and Finger et al. 2012 report on this outcome.

How long do the benefits last?

Does cataract recur? Because cataract surgery removes the eye's natural lens, cataract cannot recur in the operated eye. However, other causes of vision loss can result in blindness or visual impairment in cataract surgical patients, mitigating the benefits of cataract surgery. We have not investigated prevalence and severity of vision loss from other causes in cataract surgical patients.

Evidence from long-term follow-up. The Cataract Impact Study found that at six-year follow-up, patients who had received cataract surgery were not statistically different in quality of life from matched controls with no visual impairment at baseline.87 However, follow-up rate at six years was low (47% (n=107) for cases and 53% (n=233) for controls).88 Our understanding is that there are no other long-term follow-up studies of the impact of cataract surgery in developing countries.89

Life expectancy of cataract patients. We do not have a good understanding of the age or life expectancy demographics of people who have severe visual impairment or blindness and receive cataract surgery. As a rough estimate for our rough cost-effectiveness analysis, we rely on the age data collected through the International Eye Research Network (IERN).90 Overall, patients in this study had a median age of 65 years (IQR 58-73), and this varied by WHO region, with highest median age of 72 in the European Region and lowest median age of 60 in the Eastern Mediterranean Region.91 We are uncertain about how to interpret these differences in median age; they run counter to our intuition that in developed countries, persons with cataract have better access to surgery and hence may elect to undergo surgery at a younger age, before cataract progresses to more serious visual impairment. Of patients with severe visual impairment or blindness in the IERN dataset, 31% were aged >70, 29% 60-69, 26% 50-59, and 23% <50.92 This study does not report median age of patients with severe visual impairment or blindness, nor median age of patients restricted by country's Human Development Index (HDI). For the purpose of estimating duration of impact of cataract surgery, we estimate that the median age of persons with severe visual impairment or blindness who receive cataract surgery in a developing country is approximately 65. WHO-reported life expectancy at age 60 by World Bank income group in 2013 is 17 years in low- and lower-middle-income countries.93 Hence, we estimate the life expectancy of cataract patients with severe visual impairment or blindness to be 12 years.

Are there adverse effects?

We have not completed a thorough investigation of rates and causes of cataract surgical complications. Because we focus on visual acuity and quality of life outcomes of cataract surgery, we expect that effects of adverse outcomes of surgery are captured in our sources of key evidence. Based on rates of complications reported in studies we have reviewed for visual acuity outcomes, our impression at this stage is that high-quality cataract surgery has a low rate of long-term complications. However, our impression is that poor visual outcomes from cataract surgery are a concern in practice, when surgical quality may be variable.94 Poor visual outcome of cataract surgery may result from undetected comorbidity, or from surgical complication.

The role of comorbidities in poor visual outcome. Our understanding is that a comprehensive ocular examination prior to cataract surgery evaluates the eye for causes of visual impairment.95 Whether a person with cataract is considered for cataract surgery depends on an assessment of how much visual function they would receive from the surgery; if ocular comorbidities are causing significant visual impairment independent of the presence of a cataract, the patient may be considered a poor candidate for cataract surgery.96 Counseling and management of patient expectations about the visual outcome of their cataract surgery has been identified as an important factor in creating trust between patients (or communities) and eye care systems.97 However, in some cases comorbidity is not detected until after surgery has begun, and leads to poor post-surgical visual outcome.98

Surgically-induced astigmatism. According to the 3rd edition of the Disease Control Priorities report, surgically-induced astigmatism is the main determinant in the difference between postoperative uncorrected visual acuity and best-corrected visual acuity.99 While astigmatism can be corrected with lenses, patients in developing contexts may not have access to corrective lenses; hence it is preferable to minimize surgically-induced astigmatism. The degree of induced astigmatism may depend on surgical technique.100 We believe that by using uncorrected or presenting visual acuity as the metric of surgical outcome, we appropriately include the effect of surgically induced astigmatism on postoperative visual acuity.

Other complications. The 1986 OCTET study included the development of a weighting scale for complications of cataract surgery via expert opinion of six ophthalmologists; the scale identifies which complications are more likely to lead to drop in visual acuity or require further treatment.101 This rating of 39 complications provides a first step in identifying which serious complications of cataract surgery we may investigate further. We would likely prioritize identifying whether any surgical complications might cause future (but not immediate) loss of visual acuity, and hence not be captured in postoperative evaluations of visual acuity.

We have not closely evaluated the safety of anaesthetic used in cataract surgery. A Cochrane review concluded that both retrobulbar anaesthesia and peribulbar anaesthesia are largely effective.102

Do programs to improve access to cataract surgery work?

We have not done a thorough literature review for evidence supporting interventions to improve access to cataract surgery, but our preliminary understanding is that interventions to improve access to cataract surgery, especially in sub-Saharan Africa, have a limited track record or have been unsuccessful.103 The International Center for Eye Health (ICEH) told us that it has previously conducted a literature review to identify interventions specifically designed to improve access to cataract surgery, but found none;104 we have not examined this review. Our conversations with organizations that implement cataract-related programs have identified the following broad types of quantitative monitoring and evaluation of such programs (in no particular order):

  • Assessment of surgical quality before and after intervention using visual acuity measured preoperatively, one day after surgery, and 1-3 months after surgery.105 One organization we spoke to said that this data can be difficult to collect from facilities.106
  • District-level prevalence of cataract before and after intervention.107
  • Cataract surgical rate (CSR; number of cataract surgeries performed per million population per year) and cataract surgical coverage (CSC; proportion of the population—or of eyes—with operable cataract in a region who have received surgery) before and after intervention.108
  • Number of screenings, examinations, and/or surgeries performed per year at a facility before and after intervention.109
  • Proportion of patients who return to the hospital for cataract surgery on their second eye.110
  • Proportion of persons identified in communities and referred for surgery who attend for surgery. We have encountered wide-ranging estimated rates of uptake, which likely depend on a number of factors.111

We believe that high-quality monitoring and evaluation of these types could provide good evidence for the efficacy of a program. However, we have not yet seen or reviewed specific monitoring.

Apart from quantitative metrics of the impact of programs, large-scale long-term observation may provide some evidence about what models are successful in improving access to cataract surgery. We have not reviewed this type of evidence, but it is our understanding from a conversation with researchers from the London School of Hygiene and Tropical Medicine (LSHTM) that studies from Pakistan may demonstrate successful cataract intervention models.112

Researchers from LSHTM also cited some evidence that interventions subsidizing the cost of cataract surgery can be insufficient to reach the most disadvantaged members of a population, who may not know why they have visual impairment or blindness, or what can be done about it.113

How much does the program cost?

We have conducted a shallow literature search and found little data on the full or component costs of cataract surgery or programs to increase access to cataract surgery. We have not investigated the identified studies closely. We find it plausible that the cost of a cataract surgery (including, at the upper end of this range, outreach costs) may be $50-$100. Because we expect that reviewing a charity's cataract programs would be the best source of evidence about costs related to cataract surgery, we have not prioritized further work on this topic.

Because of the higher cost of the phacoemulsification technique for cataract surgery,114 we have focused on the costs of manual small incision cataract surgery (MSICS) in developing contexts. We are uncertain about whether programs to increase access to cataract surgery may also provide ECCE surgeries; we have not examined studies reporting costs of ECCE surgery. We expect costs of ECCE to be similar to or greater than those of MSICS.115

Lansingh, Carter, and Martens 2007, a global cost-effectiveness model of cataract surgery, includes a summary table of studies reporting costs of cataract surgery.116 This summary includes two studies (both from India) reporting on costs of MSICS. In addition, we have identified a small number of studies published since 2007 discussing the cost of cataract surgery.

  • A study of patient costs in northern Nigeria in 2013 found median total direct costs to patients (including medical and non-medical costs) of $51.117 Elsewhere, we have seen suggested that cataract surgical costs in Nigeria may be surprisingly high compared to other developing countries in Africa.118
  • The Cataract Impact Study (beginning in 2005), in which patients received ECCE or MSICS,119 reported costs of surgery in Kenya, the Philippines, and Bangladesh as $49-$74, including follow-up and medication.120
  • A 2004 study of the societal costs (obtained by summing the provider costs and the patient costs) of cataract surgery at Aravind Eye Hospital, India, estimates total costs of $40.48 for MSICS, $49.71 for ECCE, and $52.22 for PE.121 This study also mentions higher costs of cataract surgery offered by other providers.122
  • A 2003 study comparing costs in the context of a RCT comparing MSICS and ECCE techniques for cataract surgery in a hospital setting in India found costs of $20.21 for MSICS and $20.39 for ECCE from the point of view of the provider (summing facility costs and consumables).123

What do you get for your money?

We have not reviewed estimates of the cost-effectiveness of cataract surgery or cataract surgical programs from the literature. In this section, we present our rough ('back-of-the-envelope') estimate of the cost-effectiveness of cataract surgery. Based on this estimate, we cannot rule out that cataract surgery may have cost-effectiveness competitive with that of our priority programs. However, we would not be surprised if after further analysis we concluded that cataract surgery is less cost-effective than our priority programs.

Our rough estimate of cost-effectiveness

We have not completed a cost-effectiveness analysis of cataract surgery comparable to the cost-effectiveness analyses for our priority programs. Based on very rough guesses at major inputs, we estimate that cataract programs may cost $112-$1,250 per severe visual impairment reversed, which may restore quality of life comparable to peers without visual impairment for an average of about 12 end-of-life years. As discussed throughout this report, we have low confidence in these values. Based on prior experience with cost-effectiveness analyses, we expect our estimate of cost per severe visual impairment reversed to increase with further evaluation.

Benefits of cataract surgery include reversal of existing blindness or severe visual impairment, and/or prevention of future blindness or severe visual impairment. In this rough analysis, we focus on the benefit gained by converting, on average, a case of blindness or severe visual impairment (visual acuity <6/60) to a case of moderate visual impairment or better (visual acuity ≥6/60). We select this threshold based on the notion of reversing a blindness or severe visual impairment, and informed by the comparative GBD disability weights of severe visual impairment and moderate visual impairment; this conversion averts almost all the disability weight of visual impairment.

We estimate the proportion of cataract surgery patients who have bilateral blindness or severe visual impairment at 10-47% (more). We estimate success in converting blindness or severe visual impairment to moderate visual impairment of 80%-95% (more). We estimate the cost of surgery at $50-$100 (more). Hence, we estimate the cost per blindness or severe visual impairment reversed at $112-$1,250.124

We expect that the benefits of reversing blindness or severe visual impairment due to cataract last for the remainder of a patient's life expectancy, which we estimate at 12 years (more).

We discuss the magnitude of impact of cataract surgery in terms of quality of life below.

Our back-of-the-envelope estimate for the cost of a surgical outreach program per blindness or severe visual impairment reversed falls in the middle of this range: Using round estimates from our literature review of costs and our conversations with charities and experts, we suppose that a program costs $5 per person screened, that 20% of those screened receive cataract surgery at a cost of $15 for transportation and $25 for the direct cost of surgery, that 10% of those who receive surgery are blind or severely visually impaired, and that surgery is 100% effective. This program spends $650 per blindness or severe visual impairment reversed. We are highly uncertain about how close these estimated values are to the true costs and uptake of programs.

From this wide range, we conclude that cataract surgery is potentially competitive with our priority programs, but we would not be surprised if further refinement of our cost-effectiveness estimate concluded that cataract surgery is not competitive with our priority programs.

Apart from further investigation into the parameters above, our rough cost-effectiveness estimate could be improved by including an estimation of future blindness or severe visual impairment averted by cataract surgery (in addition to existing blindness or severe visual impairment reversed). Including this benefit would increase the cost-effectiveness of cataract surgery; however, we have not investigated cataract progression and we are uncertain about whether sufficient data exists to allow for estimation of the chance per year of future blindness or severe visual impairment given an operable cataract.

How much do surgeries improve quality of life?

Above, we present our rough estimate of cost per blindness or severe visual impairment reversed. In this section, we discuss the evidence for the degree to which cataract surgery patients experience improvement in quality of life.

Our preliminary understanding is that the best evidence about the effect of cataract surgery on quality of life comes from the Cataract Impact Study.125 We have not conducted a thorough search for studies of the impact of cataract surgery on quality of life; however, our impression is that the literature is sparse.126

The Cataract Impact Study found that cataract surgery raised patients' reported quality of life127 approximately to the level reported by matched controls with no visual impairment,128 despite visual acuity <6/60 in 7-15% of patients reached at one-year follow-up.129 Loss to follow-up was 12%-35%.130

We have some potential concerns with metrics of self-reported quality of life, especially in the context of receiving free or subsidized care; for example, it is possible that study participants are biased towards reporting positive post-surgical vision-related quality of life when interviewed in affiliation with the study that funded their surgery. We have not closely examined the methods of this study. We briefly discussed the Cataract Impact Study with the International Center for Eye Health (ICEH) in early 2016.131

Who is working on the program?

At this stage, we have had preliminary calls about the landscape of cataract surgical programs with the following organizations:

We discuss the types of cataract-related programs implemented by these organizations above.

Our process

We have completed a preliminary review of the landscape of cataract surgery with a focus on identifying whether the intervention is potentially competitive with our priority programs, and with a focus on identifying the most promising next steps should we decide to prioritize further investigation into this intervention. We conducted medium-depth reviews of literature on our core questions about the program in order to inform a rough back-of-the-envelope calculation of cost-effectiveness. At this stage, we believe that cataract surgery may be competitive with our priority programs. However, we retain a high degree of uncertainty, and we would not be surprised if after further work we concluded that cataract surgery is not competitive with our priority programs. Should we decide to prioritize cataract surgery for further research, we believe that the most promising next steps involve learning more about specific programs to increase access to cataract surgery.

Further questions

Questions for further research

  • How can we estimate the impact of cataract surgery on averting future blindness? (What is the likelihood that, or rate at which, non-blinding cataract progresses to blinding cataract?)
  • Is there evidence of economic benefits of cataract surgery?
  • How should we compare the benefits of cataract surgery to the benefits of our other priority programs (such as equivalent lives saved, or proportional increase in income)?
  • By how much does cataract surgery, on average, improve the visual acuity of someone with preoperative visual acuity <6/60?

Questions for a charity

  • What portion of patients served by your cataract programs have severe visual impairment or blindness before surgery?
  • Do you collect measures of preoperative and postoperative visual acuity (by patient)? What is the evidence that cataract surgeries in programs that you support yield good outcomes?
  • What are the total and component costs of cataract surgical programs?

Sources

Document Source
Aboobaker and Courtright 2016 Source (archive)
Alhassan, Kyari, and Ejere, 2015 Source (archive)
Bourne et al. 2006 Source (archive)
CDC blindness webpage Source (archive)
Chandrasekaran et al. 2008 Source (archive)
Cochrane review of MSICS vs ECCE 2014 Source (archive)
Cochrane review of MSICS vs phacoemulsification 2013 Source (archive)
Cochrane review of phacoemulsification vs ECCE 2014 Source (archive)
Congdon et al. 2013 Source (archive)
Danquah et al. 2014 Source (archive)
Essential Surgery, Disease Control Priorities 3rd Edition, 2015 Source (archive)
Essue et al. 2014 Source (archive)
Eusebio et al. 2007 Source (archive)
Finger et al. 2012 Source (archive)
Fletcher et al. 1998 Source (archive)
GiveWell’s non-verbatim summary of a conversation with CBM, February 1, 2016 Source
GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016 Source
GiveWell’s non-verbatim summary of a conversation with Sightsavers, April 14, 2016 Source
GiveWell’s non-verbatim summary of a conversation with the Fred Hollows Foundation, March 3, 2016 Source
GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016 Source
Global Health Observatory life expectancy data by World Bank income group Source (archive)
Gogate, Deshpande, and Wormald 2003 Source (archive)
Gogate et al. 2003 Source (archive)
Human Development Report 2010 Source (archive)
Ibrahim, Pozo-Martin, and Gilbert 2015 Source (archive)
ICEH webpage on the Cataract Impact Study Source (archive)
Lansingh, Carter, and Martens 2007 Source (archive)
Lewallen and Thulasiraj 2010 Source (archive)
Lindfield et al. 2009 Source (archive)
Lundqvist and Monestam 2006 Source (archive)
Mathenge et al. 2007 Source (archive)
Muralikrishnan et al. 2004 Source (archive)
Oanda's historical exchange rates EUR/USD 2015 Source
OCTET 1986 Source (archive)
Oladigbolu et al. 2014 Source (archive)
Ong, Evans, and Allan 2014 Source (archive)
Polack et al. 2010 Source (archive)
Salomon et al. 2012 Source (archive)
Shah et al. 2011 Source (archive)
Syed et al. 2013 Source (archive)
United Nations Human Development Programme website Source (archive)
US inflation calculator 2000-2016 Source (archive)
US inflation calculator 2003-2016 Source (archive)
US inflation calculator 2005-2016 Source (archive)
Venkatesh et al. 2005 (a) Source (archive)
Venkatesh et al. 2005 (b) Source (archive)
Visual Acuity Measurement Standard, 1984 Source (archive)
Wadud et al. 2006 Source (archive)
WHO Consultation on Development of Standards for Characterization of Vision Loss and Visual Functioning, 2003 Source (archive)
WHO International Statistical Classification of Diseases, Injuries and Causes of Death, 2016, H54 Source (archive)
WHO website: cataracts Source (archive)
  • 1.

    "Cataract is clouding of the lens of the eye which prevents clear vision. Although most cases of cataract are related to the ageing process, occasionally children can be born with the condition, or a cataract may develop after eye injuries, inflammation, and some other eye diseases." WHO website: cataracts.

  • 2.
  • 3.

    "According to the latest assessment, cataract is responsible for 51% of world blindness, which represents about 20 million people (2010)." WHO website: cataracts.

  • 4.

    "The treatment of cataract is surgical and very successful in restoring sight. The opaque lens is removed and replaced by an artificial intraocular lens. In many remote parts of the developing world, people remain blind from cataract, due to a lack of access to eye care." WHO website: cataracts.

  • 5.

    "The distribution of the burden of disease is disparate; 90 percent of all blind and visually impaired people live in low- and middle-income countries (LMICs) (Cunningham 2001; Thylefors 1998). A study performed in 2010 indicates that visual impairment is unequally distributed among the WHO regions (Stevens and others 2013). The bulk of the blind population resides in Asia and Sub-Saharan Africa (Pascolini and Mariotti 2012). Even in high-income countries (HICs), the prevalence is more common among the economically poorer segments of the population." Essential Surgery, Disease Control Priorities 3rd Edition, 2015, p. 197.

  • 6.

    "The prevalence of cataract as a proportion of the blind population shows large variations across countries. The figure is as low as 5 percent in developed countries such as Australia, the United Kingdom, and the United States; it is more than 55 percent in countries such as Peru and some parts of Sub-Saharan Africa (Resnikoff and others 2004)." Essential Surgery, Disease Control Priorities 3rd Edition, 2015, p. 198.

  • 7.

    For background, see the Visual Acuity Measurement Standard, 1984 and WHO Consultation on Development of Standards for Characterization of Vision Loss and Visual Functioning, 2003.

  • 8.

    "All functions of the natural lens are preserved by an IOL, with the exception of accommodation. Standard IOLs, known as monofocal IOLs, allow only distant objects to be focused and seen clearly. Patients require spectacles for near vision. This problem after cataract surgery remains a challenge for ophthalmologists. To overcome the loss of accommodation after cataract surgery, various strategies have been tried with variable success." Ong, Evans, and Allan 2014, p. 3.

  • 9.

    In other words, visual acuity of 6/6 is often described as meaning that a person can see detail from six meters to the same degree that a person with 'normal' eyesight can see from six meters.

  • 10.
    • "Many practitioners record only a visual acuity estimate, such as "hand movements" or "count fingers" when visual acuity is too low to be measured on the usual distance chart. This is not desirable. That is, meaningful visual acuity measurements in the low vision range can be made down to at least the 1/60 level. Below this level the macular area generally ceases to function and visual performance is often better characterized by visual field parameters and eccentric viewing skills than by a visual acuity value. In the lowest range, it is more desirable to use notations such as "hand motion, full field" / "hand motion in restricted field" / "light perception with projection" / "light perception, false projection" / "no reliable light perception". " Visual Acuity Measurement Standard, 1984, p. 15.
    • Notice that the WHO International Statistical Classification of Diseases, Injuries and Causes of Death, 2016, H54 uses the metrics of "counts fingers (CF) at 1 metre" and "No light perception" in its classification of severity of visual impairment.
  • 11.

    "For characterizing visual impairment for codes H54.0 to H54.3, visual acuity should be measured with both eyes open with presenting correction if any." WHO International Statistical Classification of Diseases, Injuries and Causes of Death, 2016, H54.

  • 12.

    ""Legal blindness" is defined as vision with best correction in the better eye worse than or equal to 20/200 or a visual field of less than 20 degrees in diameter." CDC blindness webpage.

  • 13.
      WHO International Statistical Classification of Diseases, Injuries and Causes of Death, 2016, H54.
    • "H54.0 Blindness, binocular Visual impairment categories 3,4,5 in both eyes"
    • "H54.1 Severe visual impairment, binocular Visual impairment category 2."
    • "H54.2 Moderate visual impairment, binocular Visual impairment category 1"
    • "H54.3 Mild or no visual impairment, binocular Visual impairment category 0."
    • "The table below gives a classification of severity of visual impairment recommended by the Resolution of the International Council of Ophthalmology (2002) and the Recommendations of the WHO Consultation on "Development of Standards for Characterization of Vision Loss and Visual Functioning" (September 2003)" In the table referenced,
      • The category "0 Mild or no visual impairment" is defined as presenting distance visual acuity equal to or better than 6/18.
      • The category "1 Moderate visual impairment" is defined as presenting distance visual acuity worse than 6/18 and equal to or better than 6/60.
      • The category "2 Severe visual impairment" is defined as presenting distance visual acuity worse than 6/60 and equal to or better than 3/60.
      • The category "3 Blindness" is defined as presenting distance visual acuity worse than 3/60 and equal to or better than 1/60 (or counts fingers (CF) at 1 metre).
      • The category "4 Blindness" is defined as presenting distance visual acuity worse than 1/60 (or counts fingers (CF) at 1 metre) and equal to or better than light perception.
      • The category "5 Blindness" is defined as no light perception.
  • 14.

    "The WHO recommends that 80% of eyes should have visual acuity better than 6/18 after surgery and that less than 5% should be worse than 6/60." Lewallen and Thulasiraj 2010, p. 4.

  • 15.

    "The International Eye Research Network (IERN), whose members are listed in Appendix A (available at: http://www.iceh.org.uk/download/attachments/15827118/iern-participants.pdf), is a newly established international collaboration of ophthalmologists. Recruitment was as follows: First, alumni of the Masters in Community Eye Health programme at the London School of Hygiene & Tropical Medicine (LSHTM) were approached by e-mail. Second, regional representatives of the IAPB, directors of international nongovernmental organizations involved in eye care and staff at the International Centre for Eye Health were asked for contacts. Third, an advertisement was placed in the Community Eye Health Journal (http://www.cehjournal.org) a quarterly publication that circulates among more than 34 000 eye care specialists in at least 180 countries.

    Potential network members were sent an invitation to participate in the study, along with information on the study’s aims and objectives. Interested respondents were sent a more detailed study protocol and a link to the web site for membership registration. Using a web-based questionnaire, network members then recorded the following information about the hospitals where they worked: type of hospital (government, private, other, etc.); volume of outpatient practice and cataract surgery in 2008; number of cataract surgeons; and status of the hospital as a provider of ophthalmology training. Information on the availability of ophthalmic ultrasound (used to assess the intraocular lens power needed) and on facilities for paediatric and vitreoretinal surgery was also collected to assess the level of specialization of each hospital, since equipment of this type is usually only available in highly specialized eye care units.

    Members with complete online registration were e-mailed a questionnaire with which to record information on the next 100 consecutive patients undergoing cataract surgery in their hospital. Supporting documents describing how to collect and enter the data were also supplied. Individuals were also asked to provide data on age, sex, literacy and patients’ preoperative VA, as well as on the date when each cataract extraction was performed. Anyone who could read, understand and sign the surgical consent form was deemed literate. All patient information was provided anonymously, without collecting any identifiers, and study documents were available in Chinese and Spanish. Members returned completed questionnaires either electronically or by regular mail."

    Shah et al. 2011, p. 750.

  • 16.

    "The VA of each patient in the better eye determined their placement into one of the following categories: blindness or severe visual impairment if VA < 6/60 (very poor visual acuity); moderate visual impairment if VA ≥ 6/60 but < 6/18; nearly normal vision if VA ≥ 6/18 but < 6/12; and normal vision if VA ≥ 6/12." Shah et al. 2011, p. 750.

  • 17.
    • See Table 2, Shah et al. 2011, p. 753.
    • Shah et al. 2011, p. 754, notes that "Although the HDI is widely used to measure a country’s level of development, its accuracy has been questioned because of wide within-country variation in the indicators used. Similarly, we could not address within-country variations in the CSR [cataract surgical rate] because WHO only provides data at the national level. The findings of our study may therefore be subject to an ecological inference fallacy and need to be interpreted with caution."
    • More on HDI: "The Human Development Index (HDI) is a summary measure of average achievement in key dimensions of human development: a long and healthy life, being knowledgeable and have a decent standard of living. The HDI is the geometric mean of normalized indices for each of the three dimensions. The health dimension is assessed by life expectancy at birth, the education dimension is measured by mean of years of schooling for adults aged 25 years and more and expected years of schooling for children of school entering age. The standard of living dimension is measured by gross national income per capita. The HDI uses the logarithm of income, to reflect the diminishing importance of income with increasing GNI. The scores for the three HDI dimension indices are then aggregated into a composite index using geometric mean." United Nations Human Development Programme website. We have not vetted this metric.
    • See Human Development Report 2010, Table 1, pp. 143-146 for the 2010 ranking of countries by HDI.
  • 18.
    • See Table 2, Shah et al. 2011, p. 753.
    • "The following categories of development were used: very high (HDI > 0.9), middle-high (> 0.6 but ≤ 0.9), middle-low (≥ 0.5 but ≤ 0.6) and low (< 0.5)." Shah et al. 2011, p. 750.
  • 19.
    • "The United Nations Human Development Index (HDI), a composite index that measures average achievement in health, education and standard of living, was used to assess each country’s socioeconomic development. The following categories of development were used: very high (HDI > 0.9), middle-high (> 0.6 but ≤ 0.9), middle-low (≥ 0.5 but ≤ 0.6) and low (< 0.5)." Shah et al. 2011, p. 750.
    • "Hospital and patient data were provided by 112 eye hospitals from 100 cities and towns in 50 countries from all six WHO regions. The African Region comprised the largest number of countries (19), followed by the Region of the Americas and the European Region (8 each). Nigeria provided the most data (from 15 hospitals), followed by Pakistan (14 hospitals) and India (11 hospitals)." Shah et al. 2011, p. 750.
    • "Although the HDI is widely used to measure a country’s level of development, its accuracy has been questioned because of wide within-country variation in the indicators used. Similarly, we could not address within-country variations in the CSR [cataract surgical rate] because WHO only provides data at the national level. The findings of our study may therefore be subject to an ecological inference fallacy and need to be interpreted with caution." Shah et al. 2011, p. 754.
  • 20.

    See totals in table 2, Shah et al. 2011, p. 753.

  • 21.

    "Members with complete online registration were e-mailed a questionnaire with which to record information on the next 100 consecutive patients undergoing cataract surgery in their hospital. Supporting documents describing how to collect and enter the data were also supplied. Individuals were also asked to provide data on age, sex, literacy and patients’ preoperative VA, as well as on the date when each cataract extraction was performed." Shah et al. 2011, p. 750. We have not seen these supporting documents.

  • 22.

    "Barriers to accessing cataract surgery include cost, distance, poor visual outcome from failed surgeries, and fear, and these barriers are often more pronounced for cataract patients who are blind or severely visually impaired. According to CBM’s surveys of partner organizations, this group only represents 10-30% of the cataract surgery population. Seeing patients tend to have better access to surgery, as they generally have greater mobility and ability to pay for surgery." GiveWell’s non-verbatim summary of a conversation with CBM, February 1, 2016, p. 3.

  • 23.
    • In Rapid Assessments of Avoidable Blindness (RAABs, sample selected via probability proportionate to size at the cluster level and compact segment sampling at the household level; see papers below for methodology) conducted as part of the the Cataract Impact Study (which is discussed further below), the number (proportion) of persons with any level of visual impairment due to cataract who had VA <6/60 with available correction was 56 (43%) in Kenya (Mathenge et al. 2007, Table 4, p. 603), 174 (50%) in Bangladesh (Wadud et al. 2006, Table 3, p. 1227; p. 3 of the pdf), and 157 (43%) in the Philippines (Eusebio et al. 2007 Table 3, p. 1590).
    • In a review of records at Aravind Eye Hospital (India) for 593 cataract surgery patients on six randomly selected days, the proportion of patients with preoperative uncorrected visual acuity <6/60 was 88.5%. Venkatesh et al. 2005 (a), p. 1081.
    • In a prospective study of 100 consecutive MSICS [manual small incision cataract surgery] patients with white cataract at Aravind Eye Hospital, India, all patients had preoperative VA <6/60. Venkatesh et al. 2005 (b), p. 174.
    • A randomized controlled trial (RCT) comparing outcomes of MSICS and ECCE at Poona Blind Men's Associations HV Desai Eye Hospital (HVDEH) in Pune, India, reports preoperative BCVA but not preoperative UCVA. Preoperatively, 85.8% of MSICS patients had VA <6/60; 86.6% of all patients (MSICS and ECCE) had preoperative VA <6/60. Because lens correction improves vision, we take this to be a lower bound on the portion of patients in that study with uncorrected or presenting VA <6/60. Gogate et al. 2003, Table 4, p. 669.
  • 24.

    As of Danquah et al. 2014, "Few studies have explored the long term impact of cataract surgery on quality of life outcomes [14,15] and no information on long-term impact on time-use or poverty indicators have been identified." (p. 2) The references are to Lundqvist and Monestam 2006 and Chandrasekaran et al. 2008 (Cited as 2007). The former is a comparison of subjective and objective visual functional results of phacoemulsification in diabetics and non-diabetics after five years, taking place in a developed country (Sweden). The latter is a comparison of self-reported health and health-related quality of life in persons who did and did not receive cataract surgery since baseline examination, with follow-up at five and ten years, taking place in a developed country (Australia). We have not closely examined these studies.

  • 25.

    The Cataract Impact Study was a case-controlled longitudinal intervention study beginning in 2005, undertaken to explore the impact of cataract surgery on health related quality of life (HRQoL), daily activities, and economic poverty among adults aged ≥50 years in Kenya, the Philippines, and Bangladesh. For an overview of the Cataract Impact Study and list of publications, see the ICEH webpage on the Cataract Impact Study. That list of publications does not include Danquah et al. 2014, and may not include additional publications since January 2013. See also further discussion of the study on this page.

    At baseline, the study identified people with cataract ("cases"), as well as age- and gender-matched controls with no visual impairment.

    • "Participants in the Cataract Impact Study were identified primarily through population-based blindness surveys which included >3600 people aged ≥50years in each setting. Clusters of 50 people aged ≥50years were selected by probability proportionate to size sampling and within clusters, households were selected using compact segment sampling. Visual acuity was assessed using tumbling E-chart the examination for cataract was conducted by an ophthalmologist using a direct ophthalmoscope. People in the survey with pinhole corrected visual acuity (VA) <6/24 in the better eye due to cataract were eligible to be cases. For each case identified, one (or up to two people in Bangladesh) age and gender matched control without visual impairment was randomly selected from the same cluster. Due to logistical and time constraints, additional case finding was undertaken in the community to increase the number of cases included." Danquah et al. 2014 p. 2.
    • "Cases were eligible for inclusion if they had best-corrected VA<6/24 in the better eye due to cataract and were aged >50 years. They were excluded if they were unable to communicate (eg, due to dementia, deafness), or it was not recommended they undergo cataract surgery (eg, serious medical illness or ophthalmic disease other than cataract thought to be the main cause of blindness)." Lindfield et al. 2009, pp. 875-6.

    Identified cases were counselled and offered cataract surgery (free in Bangladesh and Kenya; in the Philippines a fee was requested, but those who could not afford the fee were offered free surgery): "Cases were counselled and offered cataract surgery locally. Free surgery was offered in Bangladesh and Kenya. In the Philippines, a fee was requested, but those who could not afford the fee were offered free surgery." Lindfield et al. 2009, p. 876.

    The overall rate of surgical uptake was low (around 50% among cases identified outside of hospital settings).

    • "At baseline we included 196, 217 and 238 cases visually impaired from cataract and 128, 280 and 163 controls with normal vision in Kenya, Bangladesh and the Philippines respectively. Sixty percent of cases were identified through the survey, 37% through case finding and 8% from the hospital (Kenya only). All controls were recruited through the survey. Uptake of surgery among cases identified through surveys and case detection was low (88%, n = 85 in Kenya, 46% n = 117 in Bangladesh, 47% n = 112 in the Philippines)." Polack et al. 2010, p. 390.
    • "In total, 147 individuals visually impaired from cataract (82 from the survey and 65 from case detection) were recruited from Kenya, 217 (162 survey and 55 case detection) Bangladesh and 238 (146 survey and 92 case detection) the Philippines at baseline. Of these 85 (58.6%) attended for cataract surgery in Kenya, 117 (53.9%) in Bangladesh and 112 (47.1%) in the Philippines." Syed et al. 2013, p. 1662. For further discussion of predictors of attendance, see Syed et al. 2013.
    • We are uncertain what accounts for the differences in numbers between these two papers.

    This resulted in a sample of 361 patients who received surgery, 288 people with cataract who did not receive surgery, and 571 matched controls with no visual impairment.

    • See Polack et al. 2010, Table 1, p. 390. Note that the number of operated cases in Kenya includes 85 cases identified through surveys and case finding, and additional operated cases identified in hospital as per the previous footnote.
    • "Operated cases and controls were broadly similar in age, gender and marital status in the three countries, but un-operated cases were older, and more likely to be female and unmarried (Table 2). Controls were more likely than cases to be in the highest SES [socioeconomic status] quartile and have a formal education in Kenya and Bangladesh." Polack et al. 2010, p. 390.
  • 26.
    • "Participants underwent VA measurement, in daylight, with available correction, using a Snellen tumbling-E chart at 6 m or 3 m with optotype size 6/18 (20/60) and size 6/60 (20/200) on either side. Pinhole measurement was made for eyes with VA <6/18.
      Eyes with corrected VA <6/18 underwent an ophthalmic examination with torch, direct ophthalmoscope and/or slit lamp, with pupil dilation where appropriate, to diagnose the main cause of visual impairment. The WHO convention was used whereby the major cause is assigned to the disorder easiest to treat." Lindfield et al. 2009, p. 876.
    • Of people with visual impairment due to untreated cataract, in Kenya 29 (22%) had bilateral blindness (VA<3/60), 27 (21%) had bilateral severe visual impairment (3/60≤VA<6/60), and 73 (57%) had some bilateral visual impairment (6/60≤VA<6/18). See Mathenge et al. 2007, Table 4, p. 603.
    • In Bangladesh, 113 (33%) had bilateral blindness, 61 (18%) had bilateral severe visual impairment, and 171 (50%) had some bilateral visual impairment. See Wadud et al. 2006, Table 3, p. 1227 (p. 3 of the pdf).
    • In the Philippines, 99 (27%) had bilateral blindness, 58 (16%) had bilateral severe visual impairment, and 206 (57%) had some bilateral visual impairment. See Eusebio et al. 2007 Table 3, p. 1590.
  • 27.

    "VRQoL [vision-related quality of life] was assessed using the World Health Organization/ Prevention of Blindness and Deafness 20-item Visual Functioning Questionnaire (WHO/PBD VF20), which was adapted from the Indian VF33 and proposed by the WHO as a tool for assessing VRQoL in low-income settings. The scale includes 20 items on overall eyesight, visual symptoms, visual functioning and psychosocial well-being, each with a 5-point response option." Polack et al. 2010, p. 389; see that source also for more detail.

  • 28.

    "At baseline in each country, cases had considerably poorer general functioning, psychosocial and overall eyesight scores compared to controls with normal vision (P < 0.001, Table 3)." Polack et al. 2010, p. 392. See Table 3 on p. 392 for details on the magnitude and significance of these effects. For example, the largest difference in mean VRQoL scores between "operated cases" and "controls" is in "General functioning" in Bangladesh (rated 85/100 in the control group and 15/100 in the operated group), and the smallest difference is in the "Psychosocial" category in Kenya (rated 92/100 in the control group and 55/100 in the operated group).

  • 29.

    "Generic HRQoL [health-related quality of life] was assessed using the European Quality of Life (Euroqol) questionnaire. This instrument includes two components. The first consists of five descriptive domains (EQ-5D): mobility, self care, usual activity, pain/discomfort and anxiety/depression, each with three response options (no problem, some problem or extreme problem). The second measures self-rated health (SRH) using a Visual Analogue Scale (VAS), with scores ranging from 0 (representing worst imaginable health state) to 100 (best imaginable health state)." Polack et al. 2010, p. 389; see that source also for more detail.

  • 30.

    The EQ-5D categories are: Mobility, Self-care, Usual Activities, Pain/Discomfort, and Anxiety/Depression. See Polack et al. 2010, Table 4, p. 394 for magnitude and p-values at baseline of EQ-5D responses in persons with cataract who accepted surgery ("operated cases") compared to matched persons ("controls") with no visual impairment. All p-values are ≤0.001 except for pain/discomfort in patients in Bangladesh (p = 0.02). Effect sizes vary.

  • 31.

    We find it plausible that persons with cataract who refuse surgery may have generally higher quality of life than persons with cataract who accept an offer of surgery; however, for the purposes of this report we are interested in outcomes compared to baseline for people with cataract who are willing to undergo surgery, and so we do not consider the sample to be non-representative for this reason.

  • 32.

    See "Distance vision: severe impairment", "Distance vision: blindness", and "Distance vision: moderate impairment" in Salomon et al. 2012, p. 2136.

  • 33.
    • "In other cases when the description of outcomes is fairly unambiguous, we nevertheless have reported substantially lower weights than previously—eg, infertility (previously 0.18; currently 0.01), amputated fingers (previously 0.10; currently 0.03), moderate to profound hearing loss (previously 0.12-0.33; currently 0.02-0.03), and blindness (previously 0.60, currently 0.20)." Salomon et al. 2012, p. 2138.
    • "The disability weight for blindness is also substantially lower in our study than in previous GBD iterations. The decreased weight could be partly related to the use of a health construct rather than a welfare construct. In cases such as these when the difference between old and new weights is large, further empirical work to try to identify the reasons for these differences would be of high interest." Salomon et al. 2012, p. 2140.
  • 34.
      Aboobaker and Courtright 2016
    • "A systematic review of the available literature was performed using PubMed and Google Scholar. Search terms included: "Barriers, cataract, Africa, cataract surgery, cataract surgical coverage (CSC), and Rapid Assessment of Avoidable Blindness (RAAB)." The search was limited to articles published between 1999 and April 2014." (p. 145)
    • "In total, 86 articles were identified of which 12 were RAAB [Rapid Assessment of Avoidable Blindness] studies. In addition, there were 10 quantitative studies and 5 qualitative studies of barriers to utilizing cataract surgical services." (p. 146)
    • "Although the RAAB survey includes questions on barriers to cataract surgery not all publications report these findings. Among the 12 published RAAB surveys, data on barriers to cataract surgery were only available in 9 articles. Among these publications the outcomes varied considerably [Table 1]. However, variables related to awareness and access were more commonly reported than variables related to acceptance." (p. 146)
    • "The other (non‐RAAB) surveys of barriers were performed among different population groups, and not all were population‐based surveys [Graph 1]. Although there was considerable variability in the findings, cost (both direct and indirect) was the most commonly reported barrier in 6 of 10 studies." (p. 146)
    • "Finally, there were five qualitative studies of barriers [Table 2]. These studies were performed in Tanzania and Kenya. These studies suggest that complex emotional and social interactions exists within the family network that influence the mobilization of financial resources to use cataract surgery. Elderly patients place the financial needs of their children ahead of their own and do not wish to be considered a burden. The uptake of surgery was also affected by the perceived need for surgery. Males had a higher perceived need than females who tended to suffer their disability in silence. Despite the difficulty in accessing funds, these studies found that patients were willing to pay for cataract surgery. This willingness increased when knowledge of the actual cost of surgery and trust in that service improved. Cost was found to be a convenient explanation that is unchallenged by health care workers when asked about reasons for not undergoing cataract surgery. The Kenyan study found that patients with poorer visual acuity were only slightly more likely to accept cataract surgery while the lower quality of life scores were consistently associated with increased uptake of cataract surgery." (pp. 146-7)
  • 35.
  • 36.
  • 37.
  • 38.
  • 39.
  • 40.
  • 41.
  • 42.
    • "Have prior contact with the eye care institution or advance information so they come prepared (mentally and physically) to have the surgery.
    • Receive individual counseling to encourage agreement to have the procedure."

    GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, p. 2.

  • 43.

    "The primary barriers ICEH has identified to increasing CSC [cataract surgical rate] are:

    • Lack of awareness among patients that their cataracts are treatable
    • Lack of access to cataract surgery
    • High cost of cataract surgery
    • Low demand for and uptake of surgery, even among patients who are informed about it and can access it at no cost"

    GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 3.

  • 44.

    In a conversation with GiveWell in early 2016, the Fred Hollows Foundation identified workforce availability as a major barrier:

    "Common barriers include:

    • Workforce availability – A properly trained workforce is one of the biggest barriers to accessing cataract surgeries. Even when a community has an ophthalmologist, there is often no support staff, which makes the provision of eye care inefficient."

    GiveWell’s non-verbatim summary of a conversation with the Fred Hollows Foundation, March 3, 2016, p. 3.


    Sightsavers described to us its work to address supply-side challenges:
    "Sightsavers uses a "systems" approach to address both supply and demand challenges in the cataract surgery space. On the supply side, Sightsavers invests in:

    1. Human resources, including training for all cataract surgery team members, including ophthalmologists, cataract surgeons, mid-level practitioners who support the surgical team, community health workers, and technicians who maintain surgical equipment.
    2. Infrastructure, including diagnostic and surgical equipment.
    3. Consumables, including the intraocular lenses that are inserted after the cataracts are removed and post-operative eye-drops.

    GiveWell’s non-verbatim summary of a conversation with Sightsavers, April 14, 2016, p. 1.


    Researchers we spoke with at the London School of Hygiene and Tropical Medicine (LSHTM) believe that in general, creating demand for cataract surgery is a greater challenge than supplying it, and that in many places surgical capacity is not the major bottleneck to providing more surgeries:

    "In general, creating demand for the surgery is a greater challenge than supplying it. In many places, surgical capacity is not the major bottleneck to providing surgeries." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 3.

  • 45.
    • "Extracapsular cataract extraction (ECCE) was introduced with the development of microsurgical techniques in the early 1980s. The lens contents are removed through a large 12 mm incision leaving the posterior lens capsule intact. As with phacoemulsification, this keeps the anatomical barrier between the posterior and anterior segments of the eye intact and may reduce the risk of posterior segment complications. A posterior chamber IOL can then be placed in the capsular bag. If no IOL is implanted, aphakic glasses or contact lenses must be used.

      Extracapsular surgery has been the preferred method of extraction in economically disadvantaged countries and most surgeons in developing countries have been trained to use this method. ECCE may result in more induced astigmatism in the short-term compared to phacoemulsification and a longer visual rehabilitation postoperatively. Patients who have had sutured ECCE will usually need to return to have the sutures removed in clinic, in order to achieve the best visual acuity. Further technological development has led to many surgeons in developing countries adopting sutureless ECCE surgery or manual small incision cataract surgery (MSICS).

      Both sutured and sutureless ECCE leave in place the posterior capsule of the lens." Cochrane review of phacoemulsification vs ECCE 2014, p. 6.

    • "Manual small incision cataract surgery (MSICS) was first described by Blumenthal (Blumenthal 1992). In Asia and Africa there has been a renewal of interest in this technique (Ruit 2000) as an alternative to phacoemulsification because it is considerably less costly but has similar benefits of rapid visual recovery and reduced astigmatism (Yorston 2005). It involves a 6 mm to 6.5 mm scleral incision, just large enough to allow insertion of a 6 mm IOL. There are various different techniques described for performing the capsulotomy in MSICS, for example, the can-opener (Gogate 2005), the continuous curvilinear capsulorhexis (Gogate 2003) and the endocapsular technique where the incision is from pupil margin to pupil margin. The cataract is delivered into the anterior chamber, hydroextracted and aspirated. The posterior capsule of the lens is left intact. This technique is technically more difficult than a standard manual ECCE." Cochrane review of MSICS vs ECCE 2014, pp. 4-5.
    • "Phacoemulsification was first described in 1967 by Charles D. Kelman, an American ophthalmologist (1930-2004). It is the most commonly performed method of cataract extraction in the developed world. A small incision is made in the cornea (with a standard size of around 2.75 mm, but may range from 2.2 mm to 3.2 mm) and the crystalline lens is removed by ultrasonic fragmentation leaving the posterior lens capsule intact. This allows for a synthetic intraocular lens (IOL) to be inserted through the corneal incision into the capsular bag. The small incision allows rapid visual rehabilitation postoperatively and low induced astigmatism. This technique requires a phacoemulsification machine which may cost GBP 20,000 to 45,000 and the costs of required disposable equipment and maintenance are also high. Phacoemulsification requires extensive surgical training, particularly the necessity to carry out a continuous capsulorhexis." Cochrane review of phacoemulsification vs ECCE 2014, p. 6.
  • 46.
    • "Manual small incision cataract surgery (MSICS) was first described by Blumenthal (Blumenthal 1992). In Asia and Africa there has been a renewal of interest in this technique (Ruit 2000) as an alternative to phacoemulsification because it is considerably less costly but has similar benefits of rapid visual recovery and reduced astigmatism (Yorston 2005)." Cochrane review of MSICS vs ECCE 2014, pp. 4-5.
    • "Patients treated at Seva’s partner hospitals are able to choose between manual small incision cataract surgery (MSICS) and phacoemulsification. MSICS is the more affordable of the two options and is therefore more popular, particularly in rural areas where the patients served are very poor." GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, p. 4.
    • "While phacoemulsification is the main type of cataract surgery in countries like the U.S. and the United Kingdom, Sightsavers primarily supports manual small-incision cataract surgeries (MSICS). In general, ophthalmologists are already trained to conduct MSICS, and it requires less expensive equipment than phacoemulsification. In areas where Sightsavers works, cataracts are often denser, as they are diagnosed at a more advanced stage; MSICS tends to be more effective than phacoemulsification in this context." GiveWell’s non-verbatim summary of a conversation with Sightsavers, April 14, 2016, p. 2.
  • 47.

    Three recent Cochrane reviews of evidence from randomized controlled trials comparing the three cataract surgical techniques concluded that:

    • Phacoemulsification may result in better visual acuity and fewer complications than ECCE: "Removing cataract by phacoemulsification may result in a better visual acuity compared to ECCE, with a lower complication rate. The review is currently underpowered to detect differences for rarer outcomes, including poor visual outcome. The lower cost of ECCE may justify its use in a patient population where high-volume surgery is a priority, however, there are a lack of data comparing phacoemulsification and ECCE in lower-income settings." Cochrane review of phacoemulsification vs ECCE 2014, p. 2.
    • Phacoemulsification may result in better short-term uncorrected visual acuity than MSICS (but similar best-corrected visual acuity): "On the basis of this review, removing cataract by phacoemulsification may result in better UCVA in the short term (up to three months after surgery) compared to MSICS, but similar BCVA. There is a lack of data on long-term visual outcome. The review is currently underpowered to detect differences for rarer outcomes, including poor visual outcome. In view of the lower cost of MSICS, this may be a favourable technique in the patient populations examined in these studies, where high volume surgery is a priority. Further studies are required with longer-term follow-up to better assess visual outcomes and complications which may develop over time such as posterior capsule opacification." Cochrane review of MSICS vs phacoemulsification 2013, p. 2.
    • There was insufficient data comparing ECCE and MSICS to perform a meta-analysis: "We aimed to collect data on presenting visual acuity 6/12 or better and best-corrected visual acuity of less than 6/60 at three months and one year after surgery. Other outcomes included intraoperative complications, long-term complications (one year or more after surgery), quality of life, and cost-effectiveness. There were not enough data available from the included trials to perform a meta-analysis." and "Three trials randomly allocating people with age-related cataract to MSICS or ECCE were included in this review (n = 953 participants). Two trials were conducted in India and one in Nepal. Trial methods, such as random allocation and allocation concealment, were not clearly described; in only one trial was an effort made to mask outcome assessors. The three studies reported follow-up six to eight weeks after surgery. In two studies, more participants in the MSICS groups achieved unaided visual acuity of 6/12 or 6/18 or better compared to the ECCE group, but overall not more than 50% of people achieved good functional vision in the two studies. 10/806 (1.2%) of people enrolled in two trials had a poor outcome after surgery (best-corrected vision less than 6/60) with no evidence of difference in risk between the two techniques (risk ratio (RR) 1.58, 95% confidence interval (CI) 0.45 to 5.55). Surgically induced astigmatism was more common with the ECCE procedure than MSICS in the two trials that reported this outcome. In one study there were more intra- and postoperative complications in the MSICS group. One study reported that the costs of the two procedures were similar." Cochrane review of MSICS vs ECCE 2014, p. 2.
  • 48.
    • "This technique requires a phacoemulsification machine which may cost GBP 20,000 to 45,000 and the costs of required disposable equipment and maintenance are also high. Phacoemulsification requires extensive surgical training, particularly the necessity to carry out a continuous capsulorhexis." Cochrane review of phacoemulsification vs ECCE 2014, p. 6.
    • "In view of the lower cost of MSICS, this may be a favourable technique in the patient populations examined in these studies, where high volume surgery is a priority." Cochrane review of MSICS vs phacoemulsification 2013, p. 2.
    • "The lower cost of ECCE may justify its use in a patient population where high-volume surgery is a priority, however, there are a lack of data comparing phacoemulsification and ECCE in lower-income settings." Cochrane review of phacoemulsification vs ECCE 2014, p. 2.
  • 49.

    "Phacoemulsification was first described in 1967 by Charles D. Kelman, an American ophthalmologist (1930-2004). It is the most commonly performed method of cataract extraction in the developed world." Cochrane review of phacoemulsification vs ECCE 2014, p. 6.

  • 50.

    "Patients in developing countries who have other eye diseases as well as cataracts may be excluded from cataract surgery. This often depends on an assessment of how much visual function they are expected to regain from the surgery, which may take into account whether one or both eyes are affected by cataracts. In some cases, ocular comorbidities are not discovered until after the cataract surgery has been performed. For instance, during surgery, a doctor could discover a previously undiagnosed eye disease that is obscured by the cataract, which may render the surgery less effective." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 4.

  • 51.
  • 52.
  • 53.

    "There is little research-based evidence to indicate what interventions are most effective for increasing CSC [cataract surgical coverage]. ICEH conducted a literature review to identify interventions specifically designed to improve access to cataract surgery, but found none." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 4.

  • 54.
    • "In addition to building local capacity to perform high-quality surgeries, Seva supports programs to send field workers into communities to screen blind people for cataracts, because the majority of people who are blind from cataracts live in villages. This program is advertised on local radio in hopes of reaching as many people as possible. The majority of the people who are found to have cataract are referred or taken to eye hospitals for surgery. Seva funds transportation of these patients between their communities and the eye hospitals." GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, p. 2.
    • "Aravind also conducts extensive outreach by contacting non-governmental organizations (NGOs) or religious groups in a given area to inform them that Aravind will be visiting on a certain date. The local group then provides a venue and conducts marketing to inform the community of the eye care team’s upcoming visit. On the day of the visit, Aravind’s team examines all community members who assemble at the venue. Those who are blind or visually impaired from cataract are offered surgery in the eye hospital. The NGOs often provide transportation to and from the hospital for cataract surgery for those who need it." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 3.
    • "CBM also supports the outreach activities of NGOs. This might involve training community volunteers, health workers, and technicians from NGOs, or helping small NGO-run community clinics conduct screening camps where patients can be diagnosed and referred to hospitals for surgery." GiveWell’s non-verbatim summary of a conversation with CBM, February 1, 2016, p. 2. "Some of CBM’s country programs already support partners’ efforts to provide transportation services. Transportation arrangements are generally made once approximately 10 patients in an area have been diagnosed and referred for surgery. This approach may vary from country to country." (p. 3).
    • "Service delivery and medicines – transporting people to facilities where treatment is available, performing surgery, and purchasing the consumables used in surgery." GiveWell’s non-verbatim summary of a conversation with the Fred Hollows Foundation, March 3, 2016, p. 2.
  • 55.

    "Andrew Bastawrous, an ophthalmologist and lecturer at ICEH, is developing a mobile app that can be used to measure vision to identify people who are visually impaired or blind, called the Portable Eye Examination Kit (Peek). Dr. Bastawrous has also developed software that uses GPS to map the locations of people who need surgery for cataracts or trachoma. The software allows him to share with eye care providers where the highest concentrations of surgical need are located (for example, 12 people within a radius of 1–2 kilometers). The patients can then be contacted via text message and transported in groups to a hospital for surgery.

    ICEH believes that Peek has good potential as an intervention in its own right, but also as a model for testing and evaluating other interventions to improve eye care access." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 6.

  • 56.
    • Seva Foundation works with partners to provide services such as: "Building capacity in existing local hospitals. There are many hospitals with high potential in areas with high unmet need, and it can be more cost effective to improve an existing facility’s ability to deliver cataract surgery than to build a new one." GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, p. 1.
    • "Seva works with partner hospitals to build local capacity to perform safe, high-quality cataract surgeries and other eye services by sponsoring training, setting up management systems and contributing basic equipment, instruments, and medical supplies. After several years, these hospitals are able to increase the number of surgeries performed by 2-4-fold." GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, p. 2.
    • "Seva runs a volunteer exchange program through which experts in areas such as public health, ophthalmology, information technology (IT) systems, community development, or research offer training to Seva’s partners in these areas. These experts may come from within Seva’s partner network or may be from North American institutions." GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, pp. 3-4.
    • " The approach adopted in Pakistan entailed strengthening government services for cataract surgery at district level, by improving infrastructure (such as dedicated operating theatres for eye conditions), training of hospital managers, training surgeons in up-to-date surgical techniques, providing equipment for high quality surgery, and outreach support. The program has helped increase both the quality and uptake of cataract surgery, as high quality surgery is provided close to where people live. A similar approach was supported in India by the World Bank." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 5.
    • "In Pakistan, 10-12 years ago, CBM worked with the national coordinator in charge of the country’s blindness prevention program to identify district hospitals (which were often less developed than tertiary hospitals) in need of upgrades. CBM helped improve infrastructure, provide new equipment and access to consumables, and train healthcare workers such as paramedics and ophthalmologists." GiveWell’s non-verbatim summary of a conversation with CBM, February 1, 2016, p. 2.
    • "CBM’s support work is focused on the following areas:
      • Infrastructure development
      • Provision of high quality, standard equipment
      • Provision of high quality consumables
      • Human resource training
      • Cost reduction"

      GiveWell’s non-verbatim summary of a conversation with CBM, February 1, 2016, p. 1.

    • "CBM undertakes similar work with local NGOs, seeking to equip them with a high quality base health center that can do diagnoses and perform all medical, surgical and optical interventions related to cataract surgery." GiveWell’s non-verbatim summary of a conversation with CBM, February 1, 2016, p. 2.
    • "Funding for The Foundation’s comprehensive eye care programs is spread approximately equally among three components:
      • Service delivery and medicines – transporting people to facilities where treatment is available, performing surgery, and purchasing the consumables used in surgery.
      • Human resource development – training doctors, nurses, optometrists and refractionists, as well as primary care workers, community health volunteers, and teachers in eye health prevention, management and treatment.
      • Equipment and infrastructure – supplying surgical, screening, and testing equipment, and building or refurbishing facilities.

      These elements are all essential to the program’s success." GiveWell’s non-verbatim summary of a conversation with the Fred Hollows Foundation, March 3, 2016, pp. 2-3.

    • "Sightsavers uses a "systems" approach to address both supply and demand challenges in the cataract surgery space. On the supply side, Sightsavers invests in:
      1. Human resources, including training for all cataract surgery team members, including ophthalmologists, cataract surgeons, mid-level practitioners who support the surgical team, community health workers, and technicians who maintain surgical equipment.
      2. Infrastructure, including diagnostic and surgical equipment.
      3. Consumables, including the intraocular lenses that are inserted after the cataracts are removed and post-operative eye-drops."

      GiveWell’s non-verbatim summary of a conversation with Sightsavers, April 14, 2016, p. 1.

    • "Surgical care facilities are often located in major cities, and can be difficult to access for patients living in remote communities. Sightsavers aims to support efforts to increase "surgical coverage", the proportion of persons with cataract who receive surgery. This work might involve strengthening referral networks from community health workers to tertiary hospitals, building secondary hospitals, or bringing services into primary, district-level hospitals." GiveWell’s non-verbatim summary of a conversation with Sightsavers, April 14, 2016, p. 2.
  • 57.
    • "Seva supports south-to-south transfer of knowledge and skills. For example, Seva supported Nepali surgical teams’ travel to remote regions of China to perform cataract surgeries in partnership with local Chinese surgeons. Seva sponsors partners who need training to obtain it from more mature partners who offer it. This type of activity has enabled Seva to expand its programs to new countries and to build a community of service-oriented eye care institutions." GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, p. 3.
    • "Seva’s Global Sight Initiative focuses on creating a mentor-mentee relationship between underperforming eye hospitals and 12 high-performing partner hospitals that Seva has worked with extensively to develop the capacity to perform high-quality cataract surgeries. Seva works with the mentor hospitals to strengthen their ability to provide training, consulting, and planning assistance to mentee hospitals to increase the quality and quantity of cataract surgeries they perform. The mentor hospitals have been working with mentee hospitals during the last 3-4 years." GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, p. 3.
    • "Sponsoring the mentoring process involves funding assessments, training, visits between hospitals, and implementation of new management and service systems." GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, p. 5.
  • 58.

    "In another approach, an eye care team will visit a local eye unit that lacks the expertise to perform cataract surgery. The local eye unit prepares for the visit by collecting the names and contact information of people in the community who need cataract surgery. These patients are then called to return to the local unit when the visiting surgical team arrives." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 3.

  • 59.
  • 60.

    "The Fred Hollows Foundation is encouraging doctors to self-monitor by investing in tools that facilitate data capturing, sharing, and benchmarking. As part of a consortium of eye health organizations, The Foundation is developing an app called BOOST (Better Operatives Outcomes Software Tool) that allows doctors to voluntarily and confidentially report outcomes on their last 20 patients. Doctors receive information on whether their surgical outcomes are above or below average and, if below average, are asked for additional information to help identify major issues, with advice on what to do to improve outcomes.

    The organization developed the app in conjunction with Orbis International and with Aravind Eye Hospitals, which will maintain the data repository." GiveWell’s non-verbatim summary of a conversation with the Fred Hollows Foundation, March 3, 2016, p. 5.

  • 61.
    • "Seva identifies areas with large populations of people who are blind from cataract and works with local ophthalmologists and health workers to create eye health awareness and excitement about establishing a hospital. If and when the community becomes interested in building a hospital and provides land on which to build one, Seva works with other international non-governmental organizations (NGOs) to support building the hospital and to provide necessary equipment. Local entrepreneurs and philanthropists also contribute. After a hospital has been built, it is locally owned and run, not considered a ‘Seva hospital’." GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, p. 3.
    • "Surgical care facilities are often located in major cities, and can be difficult to access for patients living in remote communities. Sightsavers aims to support efforts to increase "surgical coverage", the proportion of persons with cataract who receive surgery. This work might involve strengthening referral networks from community health workers to tertiary hospitals, building secondary hospitals, or bringing services into primary, district-level hospitals." GiveWell’s non-verbatim summary of a conversation with Sightsavers, April 14, 2016, p. 2.
  • 62.

    Seva Foundation told us that it works with partners to provide services such as: "Development of comprehensive programs that deliver cataract surgery and prescription eyeglasses to those who need them." GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, p. 1.

  • 63.

    Seva Foundation told us that it works with partners to provide services such as: "Local political advocacy and funding to enable partners to work more effectively in their countries" and "Petitioning local universities to sanction ophthalmology residency training programs which meet international standards." GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, pp. 1-2.

  • 64.
  • 65.

    Very rough pooling of the results below (number of patients with postoperative VA<6/60 divided by estimated number of patients reached at follow-up who preoperatively had VA<6/60), assuming for simplicity that patients with postoperative VA<6/60 have preoperative VA<6/60 and that patients with preoperative VA<6/60 are proportionally lost to follow-up (for the purposes of estimation of the proportion of patients with preoperative VA<6/60 who achieve an outcome of VA≥6/60), yields (27 + 1 + 15)/(88.5% x 520 + 100 + 85.8% x 344) = approximately 5.0% of patients with preoperative VA<6/60 remained below that threshold after surgery; and 95.0% converted to VA≥6/60.

  • 66. "In all, 526 patients (88.5%) had a preoperative uncorrected visual acuity between perception of light (PL) and 5/60, 65 patients (11%) between 6/60 and 6/24, and two patients (0.5%) had preoperative visual acuity of 6/18 (fig 2)." Venkatesh et al. 2005 (a), p. 1081.
  • 67. "Seventy three patients (12%) were lost to follow up on the 40th postoperative day. Of the 520 patients followed up, UCVA was >6/18 for 228 (43.9%) patients, 6/24 to 6/60 for 265 (51%) patients and lesser than 6/60 for 27 (5.3%) [sic; 27/520 = 0.0519] patients (Table 4)." Venkatesh et al. 2005 (a), p. 1081.
  • 68. "Methods: In a non-comparative interventional case series, the authors reviewed the surgical outcomes of 593 patients with cataract operated upon by three high volume surgeons on six randomly selected days. There were 318 female (54%) and 275 male (46%) patients. Their mean age was 59.57 (SD 10.13) years. The majority of the patients underwent manual small incision cataract surgery (manual SICS). Extracapsular cataract extraction with posterior chamber intraocular lens (ECCE-PCIOL) and intracapsular cataract extraction (ICCE) were also done on a few patients as clinically indicated." Venkatesh et al. 2005 (a) p. 1079.
  • 69. "The pre-operative vision for all patients were either FCF (finger counting close to face) or HM (hand movements) or PL (perception of light)." Venkatesh et al. 2005 (b), p. 174.
  • 70. See Venkatesh et al. 2005 (b), Table 3, p. 175 for preoperative and 40-day UCVA by visual acuity category; at day 40, one patient (1%) had UCVA <6/60; 99 patients (99%) fell into categories ≥6/60.
  • 71. "Materials and Methods: Prospective observational study on 100 consecutive eyes of 100 patients with white cataract who had undergone MSICS with trypan blue assisted CCC. The nucleus was prolapsed into anterior chamber by using a sinskey hook and extracted out of the eye using irrigating vectis. Intraoperative and postoperative findings (according to OCTET classification) as well as postoperative visual outcomes were used as main measures to report the safety and efficacy of the surgery." Venkatesh et al. 2005 (b), p. 173.
  • 72. See Gogate et al. 2003, Table 4, p. 669 for corrected preoperative visual acuity. 85.8% of MSCIS patients had corrected preoperative visual acuity <6/60.
  • 73.
    • See Gogate et al. 2003, Table 3, p. 669 for uncorrected postoperative visual acuity outcomes. 4.3% of MSICS patients had postoperative visual acuity <6/60 at 6-week follow-up.
    • "In all, 362 of the 383 (94.5%) ECCE patients and 344 of the 358 (96.1 %) MSICS patients completed (presented for) the 6 week follow up. Their corrected and uncorrected visual acuity are as given in Tables 3 and 4. The 35 patients lost to follow up were similar on the first postoperative day." Gogate et al. 2003, p. 670.
  • 74. "Methods: In a single masked randomised controlled clinical trial, 741 patients, aged 40–90 years, with operable cataract were randomly assigned to receive either MSICS or ECCE and operated upon by one of eight participating surgeons. Intraoperative and postoperative complications were graded and scored according to the Oxford Cataract Treatment and Evaluation Team recommendations. The patients were followed up at 1 week, 6 weeks, and 1 year after surgery and their visual acuity recorded." Gogate et al. 2003, p. 667.
  • 75.

    "The WHO recommends that 80% of eyes should have visual acuity better than 6/18 after surgery and that less than 5% should be worse than 6/60." Lewallen and Thulasiraj 2010, p. 4.

  • 76.

    "ICEH found that overall quality of life tends to decline linearly with decline in visual acuity, and that quality of life improves after cataract surgery as visual acuity improves." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 2.

  • 77.

    "Methods: Cross-sectional, nationally representative sample of 16 507 adults (aged ≥30 years). Each underwent interview, logarithm of the minimum angle of resolution visual acuity (VA), autorefraction, examination of optic disc. Those with <6/12 VA on presentation underwent best-corrected VA and dilated biomicroscopic ocular examination." Bourne et al. 2006, p. 420.

  • 78.
      Bourne et al. 2006, p. 420.
    • "Results: 1317 subjects (633 men) had undergone surgery in one or both eyes. Of the 1788 operated eyes, 1099 (61%) had undergone intracapsular cataract extraction (ICCE) and 607 (34%) extracapsular surgery with an intraocular lens (ECCE+IOL). Presenting VA: 275 eyes (15.4%): 6/12 or better; 253 (14.1) <6/12 ≥ 6/18; 632 (35.3%) 6/18 to 6/60; 85 (4.8%): 6/60 to 3/60; 528 (29.5%): <3/60. With "best" refractive correction, these values were: 563 (31.5%), 332 (18.6%), 492 (27.5%), 61 (3.4%), 334 (18.7%), respectively. Of the 1498 eyes with VA ≤6/12 on presentation, 352 (23.5%) were the result of coincident disease, 800 (53.4%) refractive error, and 320 (21.4%) operative complications. Eye camp surgery (OR 1.72, p=0.002), ICCE (OR 3.78; p<0.001), rural residence (OR 1.36, p=0.01), female gender (OR 1.55, p<0.001) and illiteracy (OR 2.44, p<0.001) were associated with VA of <6/18. More recent ICCE surgeries were associated with a poorer outcome. The ratio of ECCE+IOL:ICCE in the last 3 years was 1.2:1, compared to 1:3.3 ≥4 years before the survey."
    • "Conclusion: Almost a third of cataract operations result in a presenting VA of <6/60, which could be halved by appropriate refractive correction. This study highlights the need for an improvement in quality of surgery with a more balanced distribution of services."
  • 79.
    • "In pursuance of the Vision 2020 objective of elimination of preventable causes of blindness including cataract by the year 2020, Guinness Ophthalmic Unit (GOU), Ahmadu Bello University Teaching Hospital (ABUTH), Zaria in partnership with the Kaduna State Government and Sight Savers International (SSI) provided cataract surgery to some rural communities in five Local Government Areas (LGAs) of Kaduna State (Giwa, Ikara, Kudan, Lere and Makarfi LGAs) between January 2006 and June 2007 [Figure 1]." Oladigbolu et al. 2014, p. 26.
    • "All adult cataract blind (VA < 3/60) and uniocular cataract patients screened in several villages and wards of five Local Government Areas of Kaduna State by the Community Ophthalmic Nursing Officers (CONOs) and the Community Health Extension Workers (CHEWs) between January 2006 and June 2007 were enrolled in the study." Oladigbolu et al. 2014, p. 26.
    • "A total of 690 eyes of 644 patients had extracapsular cataract extraction (ECCE) and intraocular lens (IOL) implantation in the 5 LGAs [Table 1].Forty-six patients had bilateral ECCE with IOL implants at different period (average of 4 weeks to 1year)." Oladigbolu et al. 2014, p. 27.
  • 80.
    • "Figure 3 shows the visual acuity at discharge (24-48 hours post-operative), two and eight weeks post-operative." Oladigbolu et al. 2014, p. 27. Figure 3 shows that approximately 20% of patients had visual acuity <6/60 at discharge, and nearly 10% of patients had visual acuity <6/60 at 8-week follow-up.
    • "At 2 and 8 weeks post- operative period 7.3% and 20.8% of patients respectively were lost to follow up." Oladigbolu et al. 2014, p. 27.
  • 81.
    • Postoperative outcome of cataract surgery in these studies is reported by eye and by IOL status.
    • In eyes that received cataract surgery with IOL implantation, in Kenya 64% had a 'good' outcome of visual acuity 6/18 or better with available correction, 17% had postoperative visual acuity between 6/18 and 6/60, and 19% had a 'poor' outcome of postoperative visual acuity below 6/60. See Mathenge et al. 2007, Table 7, p. 604.
    • In Bangladesh 82% had postoperative visual acuity 6/18 or better with available correction, 12% had visual acuity between 6/18 and 6/60, and 6% had visual acuity below 6/60. See Wadud et al. 2006, Table 5, p. 1228 (p. 4 of pdf).
    • In the Philippines 70% had postoperative visual acuity 6/18 or better with available correction, 16% had visual acuity between 6/18 and 6/60, and 15% had visual acuity below 6/60. See Eusebio et al. 2007, Table 6, p. 1591.
  • 82.

    "While cataract surgery can be performed in the field, evidence has shown that temporarily converting other buildings into operating facilities yields poor results compared to surgery performed in hospital." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 3.

  • 83.

    "CBM used to support surgical eye camp work. With the exception of a few remaining camps, almost all CBM-supported surgeries now take place in a hospital environment." GiveWell’s non-verbatim summary of a conversation with CBM, February 1, 2016, p. 2.

  • 84.

    "Ensuring service quality was more challenging in the past, when surgeries were primarily delivered in a temporary "camp" setting." GiveWell’s non-verbatim summary of a conversation with Sightsavers, April 14, 2016, p. 2.

  • 85.

    Congdon et al. 2013, p. e37:

    "Background Poor follow-up after cataract surgery in developing countries makes assessment of operative quality uncertain. We aimed to assess two strategies to measure visual outcome: recording the visual acuity of all patients 3 or fewer days postoperatively (early postoperative assessment), and recording that of only those patients who returned for the final follow-up examination after 40 or more days without additional prompting.

    Methods Each of 40 centres in ten countries in Asia, Africa, and Latin America recruited 40–120 consecutive surgical cataract patients. Operative-eye best-corrected visual acuity and uncorrected visual acuity were recorded before surgery, 3 or fewer days postoperatively, and 40 or more days postoperatively. Clinics logged whether each patient had returned for the final follow-up examination without additional prompting, had to be actively encouraged to return, or had to be examined at home. Visual outcome for each centre was defined as the proportion of patients with uncorrected visual acuity of 6/18 or better minus the proportion with uncorrected visual acuity of 6/60 or worse, and was calculated for each participating hospital with results from the early assessment of all patients and the late assessment of only those returning unprompted, with results from the final follow-up assessment for all patients used as the standard.

    Findings Of 3708 participants, 3441 (93%) had final follow-up vision data recorded 40 or more days after surgery, 1831 of whom (51% of the 3581 total participants for whom mode of follow-up was recorded) had returned to the clinic without additional prompting. Visual outcome by hospital from early postoperative and final follow-up assessment for all patients were highly correlated (Spearman’s rs=0.74, p<0.0001). Visual outcome from final follow-up assessment for all patients and for only those who returned without additional prompting were also highly correlated (rs=0.86, p<0.0001), even for the 17 hospitals with unprompted return rates of less than 50% (rs=0.71, p=0.002). When we divided hospitals into top 25%, middle 50%, and bottom 25% by visual outcome, classification based on final follow-up assessment for all patients was the same as that based on early postoperative assessment for 27 (68%) of 40 centres, and the same as that based on data from patients who returned without additional prompting in 31 (84%) of 37 centres. Use of glasses to optimise vision at the time of the early and late examinations did not further improve the correlations.

    Interpretation Early vision assessment for all patients and follow-up assessment only for patients who return to the clinic without prompting are valid measures of operative quality in settings where follow-up is poor."

  • 86.

    "Before beginning the cataract impact study, ICEH believed that most respondents would be receiving a high level of care from other household members, and that cataract surgery would therefore reduce family poverty by allowing those household members to return to work outside the home. Instead, the baseline survey found that most respondents, among whom the average age was 73, were not receiving extensive care from others. This finding attenuated ICEH’s predictions of poverty reduction, together with the higher than expected age of the participants. However, ICEH still found a positive impact on families’ financial circumstances one year after cataract surgery in all three countries (Kenya, the Philippines and Bangladesh), and this effect persisted at six-year follow-up. The likely mechanisms for improved finances were that after surgery the participants received less care from household members and spent more time engaged in "productive" activities." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 2. Dr. Kuper is one of the researchers involved in the Cataract Impact Study.

  • 87.
    • The Cataract Impact Study followed up with participants in Bangladesh and the Philippines at 6 years. Participants in Kenya were not followed at six years due to the small number of participants at baseline: "A third study site (Nakuru, Kenya) included in the original Cataract Impact Study was not included in the six year follow up because of the smaller study numbers recruited at baseline." Danquah et al. 2014, p. 2.
    • Vision-related quality of life of operated cases at six-year follow-up was not statistically different from vision-related quality of life of controls: "Some reductions in vision related QoL scores were observed between one and six years for both cases and controls, but scores among cases remained substantially higher than at baseline and did not differ significantly from controls at either follow up." Danquah et al. 2014, p. 4. See Table 2 on p. 4 for scores in eyesight rating, general functioning, and psychosocial categories for operated cases and controls in the Philippines and Bangladesh. The smallest p-value between cases and controls at six-year follow-up is 0.19 for eyesight rating in the Philippines.
    • General health-related quality of life also did not differ significantly. See Table 3, Danquah et al. 2014, p. 5. The most significant difference is at p=0.10 in daily activities in the Philippines.
  • 88.
      Danquah et al. 2014
    • "Response rates at six years were 47% for operated cases and 53% for controls." p. 1.
    • "The baseline survey included 217 cases and 280 controls in Bangladesh and 238 cases and 163 controls in the Philippines. Uptake of cataract surgery was generally low: 54% of cases (n = 117) identified at baseline attended for surgery by one year in Bangladesh and 47% (n=112) in the Philippines. Only a small proportion (<5%) of the un-operated cases at one year had received cataract surgery at six years and they were excluded from the analysis. At the six year follow up the response rate in Bangladesh was 48% (n = 56) for operated cases and 51% (n = 142) for controls, and in the Philippines, 45% (n = 51) for operated cases, and 56% (n=91) for controls. Of those lost to follow up 63% of cases and 56% of controls had died in Bangladesh (p = 0.32) and 75% of cases and 47% of controls had died in the Philippines (p = 0.001)." p. 4.
    • "There were few differences in socio-demographic, visual acuity, HRQoL, activity and poverty variables between participants included and lost to follow up. The exceptions were that cases lost to follow up (Bangladesh only, p = 0.04) and controls (Bangladesh p=0.04 and the Philippines p=0.007) were slightly older than those who were traced, in the Philippines male cases were slightly more likely to be lost to follow up than females (p = 0.03) and in Bangladesh cases lost to follow up spent slightly less time on productive activities (p = 0.02) (data not presented)." p. 4.
  • 89.

    As of Danquah et al. 2014, "Few studies have explored the long term impact of cataract surgery on quality of life outcomes [14,15] and no information on long-term impact on time-use or poverty indicators have been identified." (p. 2) The references are to Lundqvist and Monestam 2006 and Chandrasekaran et al. 2008 (cited as 2007). The former is a comparison of subjective and objective visual functional results of phacoemulsification in diabetics and non-diabetics after five years, taking place in a developed country (Sweden). The latter is a comparison of self-reported health and health-related quality of life in persons who did and did not receive cataract surgery since baseline examination, with follow-up at five and ten years, taking place in a developed country (Australia).

  • 90.

    Shah et al. 2011. We discuss this study, and concerns about its representativeness, above.

  • 91.

    "Patients had a median age of 65 years (IQR: 58– 73). Over one third (37%) of them were less than 50 years of age (Table 1). The oldest patients lived in the European Region (median age: 72 years), whereas the youngest lived in the Eastern Mediterranean Region (median age: 60 years)." Shah et al. 2011, p. 751.

  • 92.

    See Table 1, Shah et al. 2011, p. 751.

  • 93.

    Global Health Observatory life expectancy data by World Bank income group

  • 94.

    "Variable quality among surgeons also affects demand. In rural areas, people often learn of surgeons’ skill by word of mouth, and if they have a friend who has had a negative experience, they may be less likely to seek out the surgery themselves. Dr. Kuper highlights that poor quality of cataract surgery (and not just perceived poor quality of surgery) is in fact a major concern." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 4.

  • 95.

    "A comprehensive ocular examination evaluates the cornea, anterior chamber, pupil, lens status, retina, and optic nerve; this examination is the first step in determining the need for a surgical procedure." Essential Surgery, Disease Control Priorities 3rd Edition, 2015, p. 199.

  • 96.

    "Patients in developing countries who have other eye diseases as well as cataracts may be excluded from cataract surgery. This often depends on an assessment of how much visual function they are expected to regain from the surgery, which may take into account whether one or both eyes are affected by cataracts. In some cases, ocular comorbidities are not discovered until after the cataract surgery has been performed. For instance, during surgery, a doctor could discover a previously undiagnosed eye disease that is obscured by the cataract, which may render the surgery less effective." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 4.

  • 97.

    "Variable quality among surgeons also affects demand. In rural areas, people often learn of surgeons’ skill by word of mouth, and if they have a friend who has had a negative experience, they may be less likely to seek out the surgery themselves. Dr. Kuper highlights that poor quality of cataract surgery (and not just perceived poor quality of surgery) is in fact a major concern." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 4.

  • 98.

    "For instance, during surgery, a doctor could discover a previously undiagnosed eye disease that is obscured by the cataract, which may render the surgery less effective." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 4.

  • 99.

    "The main determinant in the difference between UCVA and BCVA is the amount of surgically induced astigmatism (SIA). SIA is the most important reason for patients to have a suboptimal UCVA, while their BCVA may be normal. The lower the SIA created, the closer UCVA and BCVA will be to each other, an ideal situation. Hence, one of the main strategies for optimizing the visual acuity of the patient is to keep the incidence of SIA as low as possible." Essential Surgery, Disease Control Priorities 3rd Edition, 2015, p. 202.

  • 100.

    "The size and location of the incision play key roles in the occurrence of SIA; larger incisions cause more SIA. A prospective Japanese study compares the SIA between two sizes of surgical incision in MSICS, 3.2 mm and 5.5 mm, and finds a reduction of SIA by 0.3 diopter when the smaller incision size is used (Kimura and others 1999). Surgical incisions created in the temporal side of the corneo-scleral junction are known to cause less SIA than the traditional superior incisions (Gokhale and Sawhney 2005; Reddy, Raj, and Singh 2007).

    Studies have also looked at the SIA created by PE and MSICS. At six months’ follow-up, Ruit and others (2007) report a mean astigmatism of 0.7 diopter for the PE group and 0.88 for the MSICS group. This difference of astigmatism was not statistically significant. At six weeks postoperatively, Gogate and others (2005) report mean astigmatism of 1.1 diopters for PE and 1.2 diopters for MSICS, which were also comparable. Other authors, however, report that PE causes significantly less SIA than MSICS at six weeks postoperatively (George and others 2005; Venkatesh and others 2010). Astigmatism caused by MSICS is greater when a superior incision is used; accordingly, it can be lessened to a great extent by using a temporal incision, thereby improving the UCVA of MSICS (Gokhale and Sawhney 2005; Kimura and others 1999)." Essential Surgery, Disease Control Priorities 3rd Edition, 2015, p. 202.

  • 101.

    "Method of devising the weighting scale:

    A list of all the complications was given to six independent observers, two of whom were ophthalmologists working in the United States. The others were from the United Kingdom and were involved with the study either as reviewers or assessors or were directly engaged in data collection.

    Each was asked to grade the complications and assign a score of 1-3 according to seriousness. Grading was done by the following rules:

    Grade 1 = Unlikely to need operation. (Score 1) or unlikely to lead to a drop in visual acuity (VA) by two lines of Snellen chart or more.

    Grade II = May need treatment. (Score 2) or may lead to some loss of vision (by two lines or more) but not suddenly.

    Grade III = Needs further treatment. (Score 3) or needs emergency action; or leads to loss of VA by two lines or more; or leads to loss of VA by two lines or more if no emergency action is taken." OCTET 1986, p. 412.

    See Table 1, OCTET 1986, p. 412, for results of the grading.

  • 102.

    "Main results: We included six trials involving 1438 participants. Three of the six trials had adequate sequence generation while all the trials had unclear allocation concealment There was no evidence of any difference in pain perception during surgery with either retrobulbar or peribulbar anaesthesia. Both were largely effective. There was no evidence of any difference in complete akinesia or the need for further injections of local anaesthetic. Conjunctival chemosis was more common after peribulbar block (relative risk (RR) 2.11, 95% confidence interval (CI) 1.46 to 3.05) and lid haematoma was more common after retrobulbar block (RR 0.36, 95% CI 0.15 to 0.88). Retrobulbar haemorrhage was uncommon and occurred only once, in a patient who had a retrobulbar block." Alhassan, Kyari, and Ejere, 2015, abstract.

  • 103.

    "The outreach models described above have not proven successful in Africa. While the Aravind model has been tested there, it has not historically worked well, as it requires a certain proportion of patients to be wealthy enough to pay for the surgery. Additionally, South Asia has more non-governmental hospitals; in Africa, the majority of cataract surgeries are performed by government hospitals, which generally lack the resources to conduct outreach activities or visits to other eye units." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 4.

  • 104.

    "There is little research-based evidence to indicate what interventions are most effective for increasing CSC [cataract surgical coverage]. ICEH conducted a literature review to identify interventions specifically designed to improve access to cataract surgery, but found none." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 4.

  • 105.
    • "The quality of a cataract surgery is assessed by measuring visual acuity before surgery, one day after surgery, and either 1 to 3 months after surgery. On a periodic basis, Seva and partners also interview patients to evaluate the impact of the surgery on quality of life." GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, p.4.
    • "Surgical outcomes: CBM assesses surgical success rate at day 1, week 1, and week 4 post-surgery using the WHO criteria for post-operative visual acuity." GiveWell’s non-verbatim summary of a conversation with CBM, February 1, 2016, p. 3.
    • "In ideal conditions, surgical outcome assessments are conducted by testing visual acuity one month following surgery. However, in settings where Sightsavers-supported surgeries take place, it can be challenging to achieve a high level of follow-up. On average, Sightsavers is able to collect this type of data for less than 20% of surgery patients. Sightsavers' projects in Asia tend to have more well-developed data collection systems than those in Africa.
      Because of challenges in assessing surgical outcome through follow-up assessments, in its new projects Sightsavers is considering assessing visual acuity one day after surgery. This proxy test would help predict one month post-surgery outcomes." GiveWell’s non-verbatim summary of a conversation with Sightsavers, April 14, 2016, p. 3.
  • 106.

    "Evaluating surgical outcomes is challenging. The WHO’s clinical guidelines call for the measurement of visual acuity immediately after surgery and again at three months, and the Fred Hollows Foundation works with hospitals to ensure that they have a system in place that adheres to these guidelines.

    However, The Foundation does not always receive this data. Some hospitals still use paper-based record-keeping systems, and while others may have more accessible data from electronic monitoring systems, surgical outcome information can be sensitive and governments in most countries are reluctant to share it with external parties." GiveWell’s non-verbatim summary of a conversation with the Fred Hollows Foundation, March 3, 2016, p. 5.

  • 107.
  • 108.

    "Cataract surgical rate (CSR) – the number of surgeries performed per million people; CSR is the key metric for evaluating cataract surgical programs". GiveWell’s non-verbatim summary of a conversation with the Fred Hollows Foundation, March 3, 2016, p. 3.

  • 109.
  • 110.

    "Given that more hospitals are being built and patients have increasingly more options, a major indicator of the perceived quality of a surgery is the percentage of patients who return to the same hospital for surgery on their second eye. A high proportion of patients treated in Seva’s partner hospitals return for their second surgery." GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, p.4.

  • 111.
  • 112.

    "Some evidence of an effective approach comes from Pakistan. ICEH conducted a study in Nigeria and Pakistan to identify and compare who needs cataract surgery in both countries, as well as to compare eye care health systems and policies in an effort to explain the differences. The study found that in Pakistan, unmarried women in rural areas had better access to cataract surgery than their counterparts in Nigeria and were less likely to be cataract-blind. This is likely because Pakistan has maintained an active program to prevent blindness over many decades with support from several international NGOs. The approach adopted in Pakistan entailed strengthening government services for cataract surgery at district level, by improving infrastructure (such as dedicated operating theatres for eye conditions), training of hospital managers, training surgeons in up-to-date surgical techniques, providing equipment for high quality surgery, and outreach support. The program has helped increase both the quality and uptake of cataract surgery, as high quality surgery is provided close to where people live. A similar approach was supported in India by the World Bank.

    Many other countries could benefit from the approach adopted in Pakistan and India, which requires a systematic approach to supporting cataract surgical services in a way that is sustainable. Increasing awareness and improving access through outreach and providing transport are other important elements." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, pp. 4-5.

  • 113.

    "Staff at ICEH believe that subsidizing cataract surgeries is effective at increasing access generally, but this approach can still fail to reach the most disadvantaged members of a population. The ICEH alumnus in northwest Nigeria conducted a research project in communities relatively near the hospital offering subsidized cataract surgery, and found that a high percentage of women in the community who were cataract blind had not accessed cataract surgery as they did not know why they were blind or what could be done about it." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 5.

  • 114.
    • "In view of the lower cost of MSICS, this may be a favourable technique in the patient populations examined in these studies, where high volume surgery is a priority." Cochrane review of MSICS vs phacoemulsification 2013, p. 2.
    • "The lower cost of ECCE may justify its use in a patient population where high-volume surgery is a priority, however, there are a lack of data comparing phacoemulsification and ECCE in lower-income settings." Cochrane review of phacoemulsification vs ECCE 2014, p. 2.
    • "Patients treated at Seva’s partner hospitals are able to choose between manual small incision cataract surgery (MSICS) and phacoemulsification. MSICS is the more affordable of the two options and is therefore more popular, particularly in rural areas where the patients served are very poor. The two techniques yield nearly identical results." GiveWell’s non-verbatim summary of a conversation with the Seva Foundation, January 13, 2016, p. 4. We do not recall discussing cataract surgical method in our other preliminary landscape calls.
  • 115.
      These studies are further discussed below.
    • Gogate, Deshpande, and Wormald 2003, a study comparing costs in the context of a RCT comparing MSICS and ECCE techniques for cataract surgery in a hospital setting in India found average costs of $15.68 for MSICS and $15.82 for ECCE from the point of view of the provider (summing facility costs and consumables). See Table 4, p. 845. Assuming that these costs are reported in 2003USD and inflating to 2016USD using a cumulative inflation rate of 1.289 as found on US inflation calculator 2003-2016 yields average provider costs of $20.21 for MSICS and $20.39 for ECCE.
    • Muralikrishnan et al. 2004, a study of the societal costs of cataract surgery at Aravind Eye Hospital, found ECCE costs to be more similar to PE costs than to MSICS costs. See Table 3, p. 375 for the table of component costs summing to total costs of 2000USD $29.40 for MSICS, 2000USD $36.10 for ECCE, and 2000USD $37.92 for PE. Subtotals for fixed provider costs, variable provider costs, direct patient costs, and indirect patient costs show that while the three surgical methods have similar direct patient costs, PE is more costly to the provider, and ECCE has greater indirect patient costs. Inflating these values from 2000USD to 2016USD using a cumulative inflation rate of 1.377 as found on US inflation calculator 2000-2016 yields societal costs of $40.48 for MSICS, $49.71 for ECCE, and $52.22 for PE.
  • 116.

    Lansingh, Carter, and Martens 2007, Table 2, p. 1673.

  • 117.
    • "Methods: Participants were those aged 17 years and above attending their first post-operative visit after first eye, subsidised, day case cataract surgery. Systematic random sampling was used to select participants who were interviewed to obtain data on socio-demographic details, and on expenditure during the assessment visit, the surgical visit, and the first follow-up visit. Costs were a) direct medical costs (patients’ costs for registration, investigations, surgery, medication), and b) direct non-medical costs (patients’ and escorts’ costs for transport, accommodation, meals). The source of funds to pay for the services received was also assessed." Ibrahim, Pozo-Martin, and Gilbert 2015, p. 1.
    • "The median total direct cost for all visits by all participants was N8,245 (US$51), being higher for men than women (N9,020; US$56 and N7,620; US$47) (p Ibrahim, Pozo-Martin, and Gilbert 2015, p. 1.
  • 118.

    Lansingh, Carter, and Martens 2007, p. 1672: "Aribaba retrospectively studied cataract surgeries, some of which were combined with other ophthalmic surgeries, in Nigeria from 2000 through 2004 and determined cost-utility using the methodology of Busbee et al. The results were similar to those of Busbee et al (Table 1), indicating that surgery costs in Nigeria are surprisingly high compared with other developing countries in Africa." We were unable to trace the citation to Aribaba 2004.

  • 119.

    "Extracapsular cataract extractions (ECCE) without biometry were undertaken in the Philippines, except for 46% of cases in Negros who received preoperative biometry. Small-incision cataract surgery (SICS) without biometry was undertaken in Kenya, and SICS with biometry was performed in Bangladesh." Lindfield et al. 2009, pp. 876-7.

  • 120.

    "Baseline surveys were undertaken between January 2005 and May 2006. In Kenya and Bangladesh free surgery was offered which was funded by this study. In the Philippines a fee was requested but those who could not afford the fee were offered free surgery. The direct cost of cataract surgery to the patient in these settings is between US$40 and $60 (inclusive of follow up and medication). In each setting, however, systems are in place to provide free surgery for those unable to pay." Polack et al. 2010, p. 388. We have assumed that these values are reported in 2005 USD, and we have converted to 2016 USD using a cumulative inflation rate of 1.225 as found on US inflation calculator 2005-2016.

  • 121.
    • See Muralikrishnan et al. 2004, Table 3, p. 375 for the table of component costs summing to total costs of 2000USD $29.40 for MSICS, 2000USD $36.10 for ECCE, and 2000USD $37.92 for PE. Subtotals for fixed provider costs, variable provider costs, direct patient costs, and indirect patient costs show that while the three surgical methods have similar direct patient costs, PE is more costly to the provider, and ECCE has greater indirect patient costs. We have inflated from 2000USD to 2016USD using a cumulative inflation rate of 1.377 as found on US inflation calculator 2000-2016.
    • "Methods: The average unit cost for each surgical procedure was calculated from the societal perspective using economic costing methods. Total annual provider’s direct costs for each input to surgery were calculated and apportioned appropriately to different cataract surgery techniques using a ‘micro-costing approach’. The patient’s direct and indirect costs for each procedure were calculated by interviewing staff and patients and by using assumptions about prices for relevant cost items such as transportation, food, medicine, spectacles and economic productivity loss." Muralikrishnan et al. 2004, p. 369.
    • For more about the micro-costing approach, see p. 371. More detail on patient costs (75 patients interviewed) are provided on p. 372. Costs to the patient included economic losses due to length of stay, and also costs for one attendant/relative to accompany the patient.
  • 122.

    "The provider’s costs of cataract surgery through various publicly funded options reported in India for Government Camps (US$41) [2016USD $56.46], State Medical College Hospitals (US$114) [2016USD $156.98] and Non Governmental Organization Hospitals (US$30) [2016USD $41.31] in 1996–97 are higher than the costs of all three surgical procedures at the Aravind Eye Hospital." Muralikrishnan et al. 2004, p. 377. Note that these are providers' costs and do not include costs to the patient. We have inflated from 2000USD to 2016USD using a cumulative inflation rate of 1.377 as found on US inflation calculator 2000-2016 and included these values in brackets.

  • 123.

    Gogate, Deshpande, and Wormald 2003, Table 4, p. 845. Average cost of surgery in US$ was $15.82 for ECCE and $15.68 for MSICS. We have assumed that these costs are reported in 2003USD and we have inflated to 2016USD using a cumulative inflation rate of 1.289 as found on US inflation calculator 2003-2016.

  • 124.

    (Cost per surgery / (Portion <6/60 pre-op x Portion ≥6/60 post-op) )

  • 125.

    We first discuss this study above. The Cataract Impact Study was a case-controlled longitudinal intervention study beginning in 2005, undertaken to explore the impact of cataract surgery on health related quality of life (HRQoL), daily activities, and economic poverty among adults aged ≥50 years in Kenya, the Philippines, and Bangladesh. For an overview of the Cataract Impact Study and list of publications, see the ICEH webpage on the Cataract Impact Study. That list of publications does not include Danquah et al. 2014, and may not include additional publications since January 2013. See also further discussion of the study on this page.

    At baseline, the study identified people with cataract ("cases"), as well as age- and gender-matched controls with no visual impairment.

    • "Participants in the Cataract Impact Study were identified primarily through population-based blindness surveys which included >3600 people aged ≥50years in each setting. Clusters of 50 people aged ≥50years were selected by probability proportionate to size sampling and within clusters, households were selected using compact segment sampling. Visual acuity was assessed using tumbling E-chart the examination for cataract was conducted by an ophthalmologist using a direct ophthalmoscope. People in the survey with pinhole corrected visual acuity (VA) <6/24 in the better eye due to cataract were eligible to be cases. For each case identified, one (or up to two people in Bangladesh) age and gender matched control without visual impairment was randomly selected from the same cluster. Due to logistical and time constraints, additional case finding was undertaken in the community to increase the number of cases included." Danquah et al. 2014 p. 2.
    • "Cases were eligible for inclusion if they had best-corrected VA<6/24 in the better eye due to cataract and were aged >50 years. They were excluded if they were unable to communicate (eg, due to dementia, deafness), or it was not recommended they undergo cataract surgery (eg, serious medical illness or ophthalmic disease other than cataract thought to be the main cause of blindness)." Lindfield et al. 2009, pp. 875-6.

    Identified cases were counselled and offered cataract surgery (free in Bangladesh and Kenya; in the Philippines a fee was requested, but those who could not afford the fee were offered free surgery): "Cases were counselled and offered cataract surgery locally. Free surgery was offered in Bangladesh and Kenya. In the Philippines, a fee was requested, but those who could not afford the fee were offered free surgery." Lindfield et al. 2009, p. 876.

    The overall rate of surgical uptake was low (around 50% among cases identified outside of hospital settings).

    • "At baseline we included 196, 217 and 238 cases visually impaired from cataract and 128, 280 and 163 controls with normal vision in Kenya, Bangladesh and the Philippines respectively. Sixty percent of cases were identified through the survey, 37% through case finding and 8% from the hospital (Kenya only). All controls were recruited through the survey. Uptake of surgery among cases identified through surveys and case detection was low (88%, n = 85 in Kenya, 46% n = 117 in Bangladesh, 47% n = 112 in the Philippines)." Polack et al. 2010, p. 390.
    • "In total, 147 individuals visually impaired from cataract (82 from the survey and 65 from case detection) were recruited from Kenya, 217 (162 survey and 55 case detection) Bangladesh and 238 (146 survey and 92 case detection) the Philippines at baseline. Of these 85 (58.6%) attended for cataract surgery in Kenya, 117 (53.9%) in Bangladesh and 112 (47.1%) in the Philippines." Syed et al. 2013, p. 1662. For further discussion of predictors of attendance, see Syed et al. 2013.
    • We are uncertain what accounts for the differences in numbers between these two papers.

    This resulted in a sample of 361 patients who received surgery, 288 people with cataract who did not receive surgery, and 571 matched controls with no visual impairment.

    • See Polack et al. 2010, Table 1, p. 390. Note that the number of operated cases in Kenya includes 85 cases identified through surveys and case finding, and additional operated cases identified in hospital as per the previous footnote.
    • "Operated cases and controls were broadly similar in age, gender and marital status in the three countries, but un-operated cases were older, and more likely to be female and unmarried (Table 2). Controls were more likely than cases to be in the highest SES [socioeconomic status] quartile and have a formal education in Kenya and Bangladesh." Polack et al. 2010, p. 390.
  • 126.
    • As of Danquah et al. 2014, "Few studies have explored the long term impact of cataract surgery on quality of life outcomes [14,15] and no information on long-term impact on time-use or poverty indicators have been identified." (p. 2) The references are to Lundqvist and Monestam 2006 and Chandrasekaran et al. 2008 (cited as 2007). The former is a comparison of subjective and objective visual functional results of phacoemulsification in diabetics and non-diabetics after five years, taking place in a developed country (Sweden). The latter is a comparison of self-reported health and health-related quality of life in persons who did and did not receive cataract surgery since baseline examination, with follow-up at five and ten years, taking place in a developed country (Australia). We have not closely examined these studies.
    • We are aware that Finger et al. 2012 and Fletcher et al. 1998 (part of the Madurai Intraocular Lens Study (MIOLS)) report on life outcomes at follow-up after cataract surgery. However, because these studies do not include controls, we believe they provide limited evidence of the impact of cataract surgery.
  • 127.

    Quality of life was measured using an adaptation of the World Health Organization/ Prevention of Blindness and Deafness 20-item Visual Functioning Questionnaire (WHO/PBD VF20) and using the European Quality of Life (Euroqol) questionnaire, composed of the EU-5D and a measure of self-rated health using the Visual Analogue Scale (VAS).

      Polack et al. 2010, p. 389.
    • "VRQoL [vision-related quality of life] was assessed using the World Health Organization/ Prevention of Blindness and Deafness 20-item Visual Functioning Questionnaire (WHO/PBD VF20), which was adapted from the Indian VF33 and proposed by the WHO as a tool for assessing VRQoL in low-income settings. The scale includes 20 items on overall eyesight, visual symptoms, visual functioning and psychosocial well-being, each with a 5-point response option."
    • "Generic HRQoL [health-related quality of life] was assessed using the European Quality of Life (Euroqol) questionnaire. This instrument includes two components. The first consists of five descriptive domains (EQ-5D): mobility, self care, usual activity, pain/discomfort and anxiety/depression, each with three response options (no problem, some problem or extreme problem). The second measures self-rated health (SRH) using a Visual Analogue Scale (VAS), with scores ranging from 0 (representing worst imaginable health state) to 100 (best imaginable health state)."
    • For more detail, see Polack et al. 2010, p. 389.
  • 128.

    As discussed above, at baseline in each country, vision-related quality of life (VRQoL) scores for people with untreated cataract (who later accepted surgery) were significantly lower in general functioning, psychosocial, and overall eyesight categories compared to controls with normal vision: "At baseline in each country, cases had considerably poorer general functioning, psychosocial and overall eyesight scores compared to controls with normal vision (P < 0.001, Table 3)." Polack et al. 2010, p. 392. See Table 3 on p. 392 for details.

    At one-year follow-up, vision-related quality of life scores remained relatively stable in the control group (with the exception of a small increase in overall eyesight scores in Bangladesh): "In contrast, scores among the controls remained relatively stable between baseline and follow-up, with the exception of a small but significant improvement in overall eyesight rating among controls in Bangladesh." Polack et al. 2010, p. 392. See Table 3 on the same page for details.

    Among cataract patients who had accepted surgery and were reached for follow-up at one year, average vision-related quality of life scores had increased substantially, from significantly lower than control group scores to approximately the level of the control group: "At follow up, among operated cases, all scores had improved substantially (by between 31 and 61 points, P<0.001, Table 3)." Polack et al. 2010, p. 392. And, "At follow up, average VRQoL scores among operated cases were approximately equal to those of control subjects with normal vision. Effect sizes were consistently large (> 1.1) for operated cases and very small among controls (< 0.2)." Polack et al. 2010n p. 393. See Polack et al. 2010, Table 3, p. 392, for details.

    In self-reported metrics of generic health-related quality of life (as measured using Euroqol), the control group's scores were broadly, but not entirely, similar between baseline and follow-up: "In contrast, baseline and follow up response distributions for controls remained broadly similar." Polack et al. 2010, p. 393. For details, see Polack et al. 2010, Table 4, p. 394. The p-values for changes in the control group are ≥0.1, with the following exceptions: pain/discomfort in Bangladesh and usual activities in the Philippines had 0.01<p<0.1; self care in Bangladesh and the Philippines, and anxiety/depression in Kenya and Bangladesh, had p<0.01.

    At baseline, the cohort of persons with cataract who accepted surgery had HRQoL scores significantly lower than those of the control group in all five EQ-5D categories, with the exception of pain/discomfort in patients in Bangladesh. (The EQ-5D categories are: Mobility, Self-care, Usual Activities, Pain/Discomfort, and Anxiety/Depression. See Polack et al. 2010, Table 4, p. 394 for magnitude and p-values at baseline of EQ-5D responses in persons with cataract who accepted surgery ("operated cases") compared to matched persons ("controls") with no visual impairment. All p-values are ≤0.001 except for pain/discomfort in patients in Bangladesh (p = 0.02). Effect sizes vary.) But at one-year follow-up, their scores were no longer different from the control group. (See Polack et al. 2010, Table 4, p. 394 for summary of EQ-5D responses at one-year follow-up in persons with cataract who accepted surgery ("operated cases") compared to matched persons ("controls") with no visual impairment. All p-values are ≥0.01. Effect sizes vary.)

    In Kenya and Bangladesh, the change in the operated group between baseline and follow-up is significant at p<0.001 in every category except pain/discomfort (p = 0.8) and anxiety/depression (p = 0.2) in Bangladesh. In the Philippines, p-values for this change are mixed: See Polack et al. 2010, Table 4, p. 394: p-values for the change in mobility, self-care, and usual activities in the operated group are 0.002-0.005, but for pain/discomfort and anxiety/depression are 0.04 and 0.02 respectively. See also: "At baseline, in each setting, more than 70% of the operated cases reported "some" or "extreme" problem with mobility, daily activities, pain/discomfort and anxiety/depression, while at least half reported problems with self-care (Table 4). At follow up, the proportion of operated cases reporting any problem reduced significantly by between 10–44% compared to baseline in all domains in Kenya and the Philippines and in mobility, daily activities and self-care in Bangladesh (Table 4)." Polack et al. 2010, p. 393.

  • 129.

    "Follow up surveys were undertaken approximately 1 year later, during the same climatic season as the baseline. All traced participants were re-examined (using same VA assessment procedures as at baseline) and re-interviewed. Interviews were conducted in respondents’ own homes (except for hospital cases in Kenya), by trained interviewers who were regularly observed by supervisors. The interviewers at baseline and follow up were the same with the exception of Bangladesh, where two additional people were trained at follow up." Polack et al. 2010, p. 389.

    See Lindfield et al. 2009, Table 3, p. 876: In patients successfully reached at one-year follow-up, postoperative visual acuity with presenting correction was <6/60 in 7%, 12%, and 15% in the Philippines, Bangladesh, and Kenya respectively.

  • 130.

    "Response rates at follow-up were generally high: 80% for operated cases, 65% for un-operated cases and 75% for controls in Kenya; 85%, 71%, 80% respectively in Bangladesh and 88%, 73%, 86% in the Philippines (Table 1). The dominant causes of non-response were person not available (moved away and untraceable or not present in the household after three visits by the survey team) or death. Refusals to participate at follow up were rare (< 3 in each country). Socio-demographic characteristics and baseline HRQoL of operated cases, un-operated and controls lost to follow-up and included at follow-up were similar (data not presented). The exception was that in the Philippines cases lost to follow up were significantly younger than those included." Polack et al. 2010, p. 390.

  • 131.

    "ICEH found that overall quality of life tends to decline linearly with decline in visual acuity, and that quality of life improves after cataract surgery as visual acuity improves. At the time of ICEH’s study, the common threshold for receiving surgery was a measured visual acuity of 6/60 or less, meaning that the respondent’s vision was approximately 10 times poorer than normal vision. However, ICEH chose to use a threshold of 6/36 and found that the surgery still had a positive impact on quality of life at this level. ICEH also found that recipients of the surgery were often pleased by the resulting increased independence even if they did not regain perfect vision." GiveWell’s non-verbatim summary of a conversation with Professor Clare Gilbert and Dr. Hannah Kuper, January 14, 2016, p. 2. See additional discussion of the Cataract Impact Study on p. 2.