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Purpose: Findings from cross-sectional blindness prevalence surveys are at risk of several biases that cause the study estimate to differ from the ‘true’ population prevalence. For example, response bias occurs when people who participate (‘responders’) differ from those who do not (‘non-responders’) in ways that affect prevalence estimates. This study aimed to assess the extent to which response bias is considered and occurs in blindness prevalence surveys in low- and middle-income countries (LMICs). Methods: We searched MEDLINE, EMBASE and Web of Science for cross-sectional blindness prevalence surveys undertaken in LMICs and published 2009-2017. From included studies, we recorded and descriptively analysed details regarding enumeration processes, response, and non-response, including the impact of non-response on results. Results: Most (95%) of the 92 included studies reported a response rate (median 91.7%, inter-quartile range 85.9-95.6%). Approximately half clearly described enumeration processes (49%), and reported at least one strategy to increase the response rate (53%); a quarter (23%) statistically compared responders and non-responders. When differential response was assessed, men were more likely to be non-responders than women. Two-thirds (65%) of the time a sociodemographic difference was found between responders and non-responders, a difference in blindness prevalence was also found. Only 13 studies (14%) commented on implications of non-response on prevalence estimates. Conclusions: Response rates are commonly reported from blindness prevalence surveys, and tend to be high. High response rates reduce—but do not eliminate—the risk of response bias. Assessment and reporting of potential response bias in blindness prevalence surveys could be greatly improved. [ABSTRACT FROM AUTHOR]

Purpose: Globally, particularly in Africa, poor compliance with medication is a major problem in glaucoma management but little is known about follow-up rates among African glaucoma patients. The aim of this study was to determine rates of follow-up among glaucoma patients attending a tertiary hospital in southern Nigeria and investigate predictors of poor follow-up. Methods: Data were extracted from medical records of new glaucoma patients who attended the hospital between June 2011 and May 2013. Socio-demographic and clinical parameters (visual acuity; stage of glaucoma) recorded at diagnosis were extracted using a pre-tested form. Follow-up was defined as good if they had attended within 9 months of the study date, inadequate when the last follow-up was more than 9 months and failed if they did not attend any follow-up or the most recent visit was more than 14 months from the study date. Univariate and multivariable analyses were undertaken to explore predictors of poor follow-up (inadequate plus failed). Results: Three hundred forty-eight patients were recruited, 54% were male and the mean age was 52.7 (range 16-88) years. Follow-up was as follows: good 28.4%, inadequate 46.6%, failed 25%. Overall, 71.6% had poor follow-up. Independent predictors of poor follow-up were poorer visual acuity (OR 3.85, 95% confidence interval (CI) 1.25-11.80 for visual impairment; OR 4.11, 95% CI 1.32-12.81 for blind) and end-stage glaucoma (OR 3.55 (1.31-9.62), p = 0.01). Conclusion: Enhanced counselling of patients with moderate to advanced glaucoma and visual impairment is required to improve follow-up and hence glaucoma management. [ABSTRACT FROM AUTHOR]

Purpose: Direct medical and non-medical costs incurred by those undergoing subsidised cataract surgery at Gusau eye clinic, Zamfara state, were recently determined. The aim of this study was to assess the willingness to pay for cataract surgery among adults with severe visual impairment or blindness from cataract in rural Zamfara and to compare this to actual costs. Methods: In three rural villages served by Gusau eye clinic, key informants helped identify 80 adults with bilateral severe visual impairment or blindness (<6/60), with cataract being the cause in at least one eye. The median amount participants were willing to pay for cataract surgery was determined. The proportion willing to pay actual costs of the (i) subsidised surgical fee (US$18.5), (ii) average non-medical expenses (US$25.2), and (iii) average total expenses (US$51.2) at Gusau eye clinic were calculated. Where participants would seek funds for surgery was determined. Results: Among 80 participants (38% women), most (n = 73, 91%) were willing to pay something, ranging from n = 41) were willing to pay US$18.5 (78% men), one-third (n = 26) were willing to pay US$25.2 (77% men); and 11% (n = 9) were willing to pay US$51.2 (all men). Only six participants (8%) already had the money to pay; one quarter (n = 20) would need to sell possessions to raise the funds. Conclusion: Willingness to pay for cataract surgery among adults with operable cataract in rural Zamfara state is far lower than current costs of undergoing surgery. People who were widowed—most of whom were women—were willing to pay least. Further financial support is required for cataract surgery to be universally accessible. [ABSTRACT FROM AUTHOR]

Purpose: Sources of avoidable waste in ophthalmic epidemiology include duplication of effort, and survey reports remaining unpublished, gaining publication after a long delay, or being incomplete or of poor quality. The aim of this review was to assess these sources of avoidable waste by examining blindness prevalence surveys undertaken in low and middle income countries (LMICs) between 2000 and 2014. Methods: On December 1, 2016 we searched MEDLINE, EMBASE and Web of Science databases for cross-sectional blindness prevalence surveys undertaken in LMICs between 2000 and 2014. All surveys listed on the Rapid Assessment of Avoidable Blindness (RAAB) Repository website (“the Repository”) were also considered. For each survey we assessed (1) availability of scientific publication, survey report, summary results tables and/or datasets; (2) time to publication from year of survey completion and journal attributes; (3) extent of blindness information reported; and (4) rigour when information was available from two sources (i.e. whether it matched). Results: Of the 279 included surveys (from 68 countries) 186 (67%) used RAAB methodology; 146 (52%) were published in a scientific journal, 57 (20%) were published in a journal and on the Repository, and 76 (27%) were on the Repository only (8% had tables; 19% had no information available beyond registration). Datasets were available for 50 RAABs (18% of included surveys). Time to publication ranged from <1 to 11 years (mean, standard deviation 2.8 ± 1.8 years). The extent of blindness information reported within studies varied (e.g. presenting and best-corrected, unilateral and bilateral); those with both a published report and Repository tables were most complete. For surveys published and with RAAB tables available, discrepancies were found in reporting of participant numbers (14% of studies) and blindness prevalence (15%). Conclusion: Strategies are needed to improve the availability, consistency, and quality of information reported from blindness prevalence surveys, and hence reduce avoidable waste. [ABSTRACT FROM PUBLISHER]

Background: Blindness from glaucoma is associated with socio-economic deprivation, presumed to reflect poor access to care and poor adherence to treatment. Objectives: To determine why people with glaucoma are presenting late for treatment and to understand access to glaucoma care. Additionally, we sought to identify what patients and the community know, do and think about the condition and why the poor are the most affected with glaucoma blindness. Design: Study participants were from four communities and two hospitals in Abuja-FCT and Kaduna State, Nigeria. A total of 120 participants were involved, including 8 focus group discussions, 7 in-depth interviews with blind/visually impaired glaucoma patients, 5 rapid direct observation visits with these patients and 13 exit interviews of glaucoma patients in the hospital. The data were analysed using content analysis, interpreting participant experiences in terms of three key steps conceptualised as important in the care pathway: what it takes to know glaucoma, to reach a diagnosis and to access continued care. Results: This article presents multiple narratives of accessing and maintaining glaucoma care and how people manage and cope with the disease. People may be presenting late due to structural barriers, which include lack of knowledge and awareness about glaucoma and not finding an appropriately equipped health care facility. What keeps glaucoma patients within the care pathway are a good hospital experience; a support structure involving family, counselling and shared patients’ experiences; and an informed choice of treatment, as well as agency. The high cost of purchasing care is a major factor for patients dropping out of treatment. Conclusion: The findings suggest the need to address economic and social structural drivers as glaucoma presents another case study to demonstrate that poverty is a strong driver for blindness. There is also a need for clear glaucoma care pathways with early case finding in the community, two-way referral/feedback systems, well-equipped glaucoma care hospitals and better eye health care financing. [ABSTRACT FROM AUTHOR]

Purpose: The World Health Organization Program for the Prevention of Blindness adopted the principles of universal health coverage (UHC) in its latest plan, Universal Eye Health: A Global Action Plan, 2014–2019. This plan builds on the achievements of Vision 2020,which aimed to reduce the global prevalence of avoidable blindness, and its unequal distribution, by the year 2020. Methods: We reviewed the literature on health equity and the generation and use of evidence to promote equity, particularly in eye health. We describe the nature and extent of the equity-focused evidence to support and inform eye health programs on the path to universal eye health, and propose ways to improve the collection and reporting of this evidence. Results: Blindness prevalence decreased in all regions of the world between 1990 and 2010, albeit not at the same rate or to the same extent. In 2010, the prevalence of blindness in West Africa (6.0%) remained 15 times higher than in high-income regions (0.4%); within all regions, women had a higher prevalence of blindness than men. Beyond inter-regional and sex differences, there is little comparable data on the distribution of blindness across social groups within regions and countries, or on whether this distribution has changed over time. Similarly, interventions known to address inequity in blindness are few, and equity-relevant goals, targets and indicators for eye health programs are scarce. Conclusion: Equity aims of eye health programs can benefit from the global momentum towards achieving UHC, and the progress being made on collecting, communicating and using equity-focused evidence. [ABSTRACT FROM AUTHOR]

Purpose: Poverty can be a cause and consequence of blindness. Some causes only affect the poorest communities (e.g. trachoma), and poor individuals are less likely to access services. In low income countries, cataract blind adults have been shown to be less economically active, indicating that blindness can exacerbate poverty. This study aims to explore associations between poverty and blindness using national survey data from Nigeria. Methods: Participants ≥40 years were examined in 305 clusters (2005–2007). Sociodemographic information, including literacy and occupation, was obtained by interview. Presenting visual acuity (PVA) was assessed using a reduced tumbling E LogMAR chart. Full ocular examination was undertaken by experienced ophthalmologists on all with PVA <6/12 in either eye. Causes of vision loss were determined using World Health Organization guidelines. Households were categorized into three levels of poverty based on literacy and occupation at household level. Results: A total of 569/13,591 participants were blind (PVA <3/60, better eye; prevalence 4.2%, 95% confidence interval [CI] 3.8–4.6%). Prevalences of blindness were 8.5% (95% CI 7.7–9.5%), 2.5% (95% CI 2.0–3.1%), and 1.5% (95% CI 1.2–2.0%) in poorest, medium and affluent households, respectively (p = 0.001). Cause-specific prevalences of blindness from cataract, glaucoma, uncorrected aphakia and corneal opacities were significantly higher in poorer households. Cataract surgical coverage was low (37.2%), being lowest in females in poor households (25.3%). Spectacle coverage was 3 times lower in poor than affluent households (2.4% vs. 7.5%). Conclusion: In Nigeria, blindness is associated with poverty, in part reflecting lower access to services. Reducing avoidable causes will not be achieved unless access to services improves, particularly for the poor and women. [ABSTRACT FROM AUTHOR]

Purpose: To determine normative values for defining glaucoma in cross-sectional surveys in Nigerian adults. Methods: Multistage stratified cluster random sampling with probability-proportional-to-size procedures to select a nationally representative sample of 15,027 persons aged ≥40 years in 305 clusters across Nigeria. Systematic sampling of 1 in 7 participants gave 1759 who were examined in detail to construct a normative database. The normative subset was used to determine values for vertical cup/disc ratio (VCDR) and intraocular pressure (IOP) for glaucoma diagnosis according to the International Society of Geographical and Epidemiological Ophthalmology (ISGEO) criteria. Examinations included visual field testing by frequency doubling technology (FDT), Goldmann applanation tonometry, and optic disc image grading by Moorfields Eye Hospital Reading Centre. Results: In the normative dataset, 1057/1759 persons (60.1%) had normal FDTs, and constituted the hypernormal. Of these, 851 had VCDR and 973 had IOP measurements taken in both eyes. For category 1 (structural and functional evidence of glaucoma), the 97.5th percentile VCDR was 0.7. For category 2 (advanced structural damage with unproven visual field loss), the 99.5th percentile VCDR was 0.75. In addition, asymmetry in VCDR was 0.1 difference at the 97.5th percentile and 0.2 difference at the 99.5th percentile. Category 3 criteria were used when the optic disc was not visible and field testing not possible; 99.5th percentile IOP is one criterion (28 mmHg). Conclusion: While these results do not differentiate between open-angle and angle-closure mechanisms, they can be applied to determine the prevalence of glaucoma in Nigeria and sub-Saharan African countries with similar sociodemographic characteristics. [ABSTRACT FROM AUTHOR]

Purpose: Since the Declaration of Alma Ata, universal coverage has been at the heart of international health. The purpose of this study was to review the evidence on factors and interventions which are effective in promoting coverage and access to cataract and other health services, focusing on developing countries. Methods: A thorough literature search for systematic reviews was conducted. Information resources searched were Medline, The Cochrane Library and the Health System Evidence database. Medline was searched from January 1950 to June 2010. The Cochrane Library search consisted of identifying all systematic reviews produced by the Cochrane Eyes and Vision Group and the Cochrane Effective Practice and Organisation of Care. These reviews were assessed for potential inclusion in the review. The Health Systems Evidence database hosted by MacMaster University was searched to identify overviews of systematic reviews. Results: No reviews met the inclusion criteria for cataract surgery. The literature search on other health sectors identified 23 systematic reviews providing robust evidence on the main factors facilitating universal coverage. The main enabling factors influencing access to services in developing countries were peer education, the deployment of staff to rural areas, task shifting, integration of services, supervision of health staff, eliminating user fees and scaling up of health insurance schemes. Conclusion: There are significant research gaps in eye care. There is a pressing need for further high quality primary research on health systems-related factors to understand how the delivery of eye care services and health systems' capacities are interrelated. [ABSTRACT FROM AUTHOR]

Purpose: Type 2 idiopathic macular telangiectasia (MacTel) is a progressive retinal disease associated with a slow deterioration of visual acuity, starting in the fifth to seventh decades of life. The etiology and pathogenesis of the disease are little known, and no effective therapy is available. We aimed to estimate the prevalence and describe the phenotype of type 2 MacTel in two African populations. Methods: From two population-based cross-sectional surveys conducted nationally in Nigeria and in the Nakuru district of Kenya, patients with fundus features of type 2 MacTel were selected. Diagnosis was based on color fundus images, grading performed according to the MacTel Study protocol and staged using the Gass and Blodi system. Disease phenotype and clinical characteristics of affected participants were assessed. Results: Of 8599 total participants, five showed a phenotype compatible with type 2 MacTel. Prevalence was estimated as 0.06% (95% confidence interval [CI] 0.02-0.21%) in Kenya, 0.06% (95% CI 0.01-0.17%) in Nigeria, and overall at 0.06% (95% CI 0.02-0.14%). Mean age was 62 years (SD 5 years), four of five affected participants were female, and none had a history of diabetes. Median corrected visual acuity was 6/12 in the better eye and 6/69 in the worse eye. Conclusions: The estimated prevalence and phenotype of type 2 MacTel in the African populations examined were similar to those in predominantly white populations. All data published so far are based on the analysis of color fundus images only and are thus likely to underestimate the true prevalence of this disease. [ABSTRACT FROM AUTHOR]

Purpose: To determine cataract surgical coverage, and barriers to modern cataract surgery in Nigeria. Methods: Multistage stratified cluster random sampling was used to identify a nationally representative sample of 15,027 persons aged 40++ years. All underwent visual acuity testing, frequency doubling technology visual field testing, autorefraction, and measurement of best corrected vision if <6/12 in one or both eyes. An ophthalmologist examined the anterior segment and fundus through an undilated pupil for all participants. Participants were examined by a second ophthalmologist using a slit lamp and dilated fundus examination using a 90 diopter condensing lens if vision was <6/12 in one or both eyes, there were optic disc changes suggestive of glaucoma, and 1 in 7 participants regardless of findings. All those who had undergone cataract surgery were asked where and when this had taken place. Individuals who were severely visually impaired or blind from unoperated cataract were asked to explain why they had not undergone surgery. Results: A total of 13,591 participants were examined (response rate 89.9%). Prevalence of cataract surgery was 1.6% (95% confidence interval 1.4-1.8), significantly higher among those aged ≥70 years. Cataract surgical coverage (persons) in Nigeria was 38.3%. Coverage was 1.7 times higher among males than females. Coverage was only 9.1% among women in the South-South geopolitical zone. Over one third of those who were cataract blind said they could not afford surgery (36%). Conclusions: Cataract surgical coverage in Nigeria was among the lowest in the world. Urgent initiatives are necessary to improve surgical output and access to surgery. [ABSTRACT FROM AUTHOR]

Purpose: To examine the relationship between education, other risk factors and incident primary angle closure glaucoma (PACG). Method: Glaucoma was excluded in a group of 4597 Mongolian volunteers in 1999. After 6 years, 1892 traced participants had full ophthalmic examination, dilated disc photographs and agreed to complete a questionnaire on socio-economic status. PACG was diagnosed using both structural and functional evidence from objective grading of paired disc photographs, follow up visual fields and clinical examination. Ophthalmic examination included van Herick grading, Goldmann intraocular pressure (IOP), gonioscopy, lens opacity grading and dilated disc examination. Central anterior chamber depth, lens thickness and axial length were recorded using ultrasound A scan mounted on a slitlamp. Education level was assessed using national census categories. Results: PACG was diagnosed in 29 participants (6 year incidence == 1.53%, 95% confidence interval (CI) == 1.03-2.19%). In univariate analysis, risk factors for incident PACG included presence of refractive error, narrow van Herick grading of ≤15%, narrower average Shaffer grading, higher IOP, larger cup disc ratio and lower levels of education. In multivariate analysis, adjusted for age, sex, Shaffer grading, refractive error and IOP, those with no formal education were approximately 7 times more likely to develop PACG compared to those with >8 years of formal schooling (OR == 7.27, 95% CI == 2.73-19.38). Conclusions: People with lower levels of education have a higher risk of incident PACG, independent of age, sex, IOP and axial length. [ABSTRACT FROM AUTHOR]

Purpose: To assess visual functioning and quality of life in a representative sample of normally sighted, visually impaired and cataract operated individuals aged ≥ 30 years in Pakistan. Methods: As part of the Pakistan National Blindness and Visual Impairment Survey, visual functioning (VF) and quality of life (QOL) questionnaires were administered to participants with presenting visual acuity less than 6/60 in either eye, aphakes/pseudophakes and a phakic sample with normal acuity (≥ 6/12 both eyes). Results: Of 16,507 adults included in the survey, 2329 questionnaires were administered. There were strong correlations between visual acuity and VF/QOL. Mean VF and median QOL scores in normally sighted phakic individuals were 81.1 and 88.9, respectively, but were only 34.8 and 64.9 in blind unoperated individuals. In the cataract operated population overall mean VF and median QOL scores were 49.3 and 75.0. Both VF and QOL scores were lower in operated individuals than unoperated individuals (p < 0.001). Among operated individuals, rural dwelling and illiteracy were associated with lower VF and QOL scores (p all < 0.02). Although in multivariable analysis bilateral pseudophakes had similar VF scores to bilateral aphakes they had significantly better QOL scores (p = 0.001). Conclusions: Cataract surgery in Pakistan has not led to VF and QOL scores equivalent to those in unoperated individuals with the same levels of visual acuity. The higher proportion of intraocular lens surgery in recent years is likely to improve QOL following cataract surgery. Further focus is needed on rural and illiterate populations, to ensure that they achieve comparable VF/QOL outcomes following surgery. [ABSTRACT FROM AUTHOR]

Purpose: To determine the prevalence of refractive error (RE) and spectacle wear and to explore the need for spectacle correction in adults (30 years or older) in Pakistan. Methods: Multi-stage, cluster random sampling national survey. Each subject had their medical history taken, visual acuity measured, and underwent autorefraction, biometry and fundus examination. Those that presented with visual acuity of less than 6/12 in either eye underwent more detailed examination, including corrected distance visual acuity measurement (autorefraction results placed in a trial lens frame). Myopia was defined as a spherical equivalent of worse than -0.5D, hypermetropia as greater than +0.5D, and astigmatism as greater than 0.75D. Spectacle need (i.e., those that improved from unaided VA with spectacle correction) was determined along with the spectacle coverage, defined as the proportion of need that was met (by the participant's own spectacles). Results: The crude prevalence of myopia, hypermetropia and astigmatism was 36.5%, 27.1%, and 37%, respectively. The prevalence of spectacle wear in phakic participants was 4.0%, significantly lower than for those who were pseudo/aphakic (41.7%). Just over a quarter (25.8%) of spectacle wearers presenting with visual impairment (< 6/12) were able to improve their vision when retested with their autorefraction prescription. The overall spectacle coverage (6/12 cutoff) was 15.1%. Conclusions: This survey provides the first reliable national estimates. RE services are not covering the majority of the population in need and the provision of spectacle correction, as a highly cost effective treatment for visual impairment, needs addressing within the country's national eye care program. [ABSTRACT FROM AUTHOR]

Identifies the environmental factors associated with coloboma, a congenital defects in the eye in India. Rate of visual morbidity in children in the country; Geographical variations in the prevalence of congenital eye anomalies; Categories in the etiology of coloboma.

BACKGROUND. The prevalence and causes of blindnessin children vary widely between regions. Few epidemiological data are availableon the relative importance of the major congenital anomalies of the globe(i.e., microphthalmos, anophthalmos, coloboma) as causes of blindness in children.The aim of this study was to determine the re-gional variation in the proportionof severe visual impairment and blindness due to congenital abnormalitiesof the globe in children in schools for the blind and in those identifiedthrough Community Based Rehabilitation programs. Other objectives were toestimate the prevalence of blindness due to major congenital abnormalities,and to investigate their etiology. METHODS. Data on the causes of blindness in children were collected between1990 and 1998 using standard methods, definitions and reporting form in 26countries. Children were examined in schools for the blind and in CommunityBased Rehabilitation programs. RESULTS. Of 7,113 children aged 3-15 years with severe visual impairmentand blindness examined, 762 (10.7%) had microphthalmos, 161 (2.3%) had anophthalmos,and 96 (1.3%) had coloboma. There are large regional differences in the proportionof severe visual loss in blind school children, ranging from 1.4% in Cubato 33.2% in Sri Lanka. Severe visual loss due to congenital abnormalitiesof the globe is estimated to affect between 0.4 and 16.2/100,000 childrenin the countries studied. An underlying cause could not be identified in 84.2%. CONCLUSIONS. Major congenital abnormalities of the globe are importantcauses of severe visual loss in children, particularly in Asian countries.Further research into etiology is warranted in order to plan prevention programs. [ABSTRACT FROM AUTHOR]