Hans Limburg

Rapid Assessment of Avoidable Blindness in Western Rwanda: Blindness in a Postconflict Setting

Background The World Health Organization estimates that there were 37 million blind people in 2002 and that the prevalence of blindness was 9% among adults in Africa aged 50 years or older. Recent surveys indicate that this figure may be overestimated, while a survey from southern Sudan suggested that postconflict areas are particularly vulnerable to blindness. The aim of this study was to conduct a Rapid Assessment for Avoidable Blindness to estimate the magnitude and causes of visual impairment in people aged ≥ 50 y in the postconflict area of the Western Province of Rwanda, which includes one-quarter of the population of Rwanda. Methods and Findings Clusters of 50 people aged ≥ 50 y were selected through probability proportionate to size sampling. Households within clusters were selected through compact segment sampling. Visual acuity (VA) was measured with a tumbling “E” chart, and those with VA below 6/18 in either eye were examined by an ophthalmologist. The teams examined 2,206 people (response rate 98.0%). The unadjusted prevalence of bilateral blindness was 1.8% (95% confidence interval [CI] 1.2%–2.4%), 1.3% (0.8%–1.7%) for severe visual impairment, and 5.3% (4.2%–6.4%) for visual impairment. Most bilateral blindness (65%) was due to cataract. Overall, the vast majority of cases of blindness (80.0%), severe visual impairment (67.9%), and visual impairment (87.2%) were avoidable (i.e.. due to cataract, refractive error, aphakia, trachoma, or corneal scar). The cataract surgical coverage was moderate; 47% of people with bilateral cataract blindness (VA < 3/60) had undergone surgery. Of the 29 eyes that had undergone cataract surgery, nine (31%) had a best-corrected poor outcome (i.e., VA < 6/60). Extrapolating these estimates to Rwandas Western Province, among the people aged 50 years or above 2,565 are expected to be blind, 1,824 to have severe visual impairment, and 8,055 to have visual impairment. Conclusions The prevalence of blindness and visual impairment in this postconflict area in the Western Province of Rwanda was far lower than expected. Most of the cases of blindness and visual impairment remain avoidable, however, suggesting that the implementation of an effective eye care service could reduce the prevalence further.

Cataract blindness in Paraguay – results of a national survey

PURPOSE To estimate the burden of visual loss and blindness due to cataract in people aged 50 years and over in Paraguay. METHODS Forty clusters of 60 persons each who were 50 years and older (2400 eligible persons) were selected by systematic random sampling from the entire population of Paraguay.A total of 2136 persons were examined (89% coverage). RESULTS For the population 50 years and over, the age- and gender- adjusted prevalence of bilateral blindness (VA < 3/60 with available correction) was 3.14% (95% CI: 2.2–4.4). The adjusted prevalence of bilateral cataract blindness (VA < 3/60) was 2.01% (95% CI: 1.3–3.0), making cataract the major cause of bilateral blindness in this age group (64%). The adjusted prevalence of bilateral severe visual impairment (VA < 6/60 with available correction) was 5.17% (95% CI: 3.9–6.7) and the adjusted prevalence of severe visual impairment due to bilateral cataract (VA < 6/60) was 3.09% (95% CI: 2.2–4.3). The cataract surgical coverage (persons) was 44% for bilaterally blind persons with VA < 3/60; 36% for persons with bilateral VA < 6/60; and 28% for any eye with VA < 6/60 due to cataract. With IOL implantation, 77% of the operated eyes could see 6/18, against 46% of the non-IOLs (p < 0.005), a significant better outcome. CONCLUSIONS There is a need to increase the cataract surgical coverage in Paraguay. The number of eye surgeons is adequate but the accessibility of cataract surgical services in rural areas and the affordability of surgery to large sections of society are major constraints.

Review of recent surveys on blindness and visual impairment in Latin America

Aims: To review recent data on prevalence and causes of blindness and visual impairment in Latin America. Method: Data from recent population-based prevalence surveys in nine countries in Latin America, covering 30 544 people aged 50 years and older, are presented. Results: The prevalence of bilateral blindness (VA <3/60 in the better eye with available correction) ranged from 1.3% in urban Buenos Aires, Argentina, to 4.0% in two rural districts of Peru; low vision from 5.9% in Buenos Aires to 12.5% in rural Guatemala. Cataract was the main cause of blindness (41–87%), followed by posterior segment disease (7–47%). Avoidable blindness ranged from 43% in urban Brazil to 94% in rural Guatemala. Conclusions: 43% to 88% of all blindness in Latin America is curable, being caused by cataract and refractive errors. Simple and cost-effective intervention strategies exist and need to be made available to more people. Also, the visual outcome from cataract surgery can be improved. In the urban areas with adequate eye care services, blindness and low vision due to posterior segment disease are increasing. Results from these surveys may help planners to estimate the prevalence and causes of blindness in their own area or country.

Rapid Assessment of Avoidable Blindness and Needs Assessment of Cataract Surgical Services in Satkhira District, Bangladesh.

Aims: To estimate the magnitude and causes of blindness in people aged ⩾50 years in Satkhira district, Bangladesh, and to assess the availability of cataract surgical services. Methods: 106 clusters of 50 people aged ⩾50 years were selected by probability-proportionate to size sampling. Households were selected by compact segment sampling. Eligible participants had their visual acuity measured. Those with visual acuity <6/18 were examined by an ophthalmologist. A needs assessment of surgical services was conducted by interviewing service providers. Results: 4868 people were examined (response rate 91.9%). The prevalence of bilateral blindness was 2.9% (95% confidence interval (CI) 2.4% to 3.5%), that of severe visual impairment was 1.6% (95% CI 1.2% to 2.0%) and that of visual impairment was 8.4% (95% CI 7.5% to 9.3%). 79% of bilateral blindness was due to cataract. The cataract surgical coverage was moderate; 61% of people with bilateral cataract blindness (visual acuity <3/60) had undergone surgery. 20% of the 213 eyes that had undergone cataract surgery had a best-corrected poor outcome (visual acuity <6/60). The cataract surgical rate (CSR) in Satkhira was 547 cataract surgeries per million people per year. Conclusions: Although the prevalence of blindness and visual impairment was lower than expected, the CSR is inadequate to meet the existing need, and the quality of surgery needs to be improved.

Routine monitoring of visual outcome of cataract surgery. Part 2: Results from eight study centres.

Aim: To determine whether monitoring of cataract outcome can be implemented as a routine activity in different hospital settings in Africa and Asia, and to assess the impact of routine monitoring. Methods: Eight eye centres in Asia and Africa were involved in the study between 1 June and 31 December 2000. Seven centres used a specifically designed cataract surgery record form with computerised data entry and analysis (CCSRF), and one centre used a manual recording form (MCSRF). Data were used to evaluate quality of data entry, follow up after surgery, and to assess trends in the proportion of complications and visual outcome after surgery. Findings: The reporting systems were accepted and used by all centres, and data were recorded for 5198 cataract operations. Overall, 54% of eyes were followed for 8 weeks or more and 41% for 6 months. Follow up rates varied between centres from nil to almost 100%. Visual acuity tended to improve over time. The outcome could be improved at all follow up periods by providing best spectacle correction. At 8 weeks or more follow up, surgical complications or inadequate spectacle correction accounted for 72% of the causes of poor outcome. Three centres showed a significant reduction in complication rates over the course of the 6 month study. Data entry was identified as a problem and the CCSRF software has been modified to include consistency checks to reduce data entry errors. Conclusion: A simple system to monitor cataract outcome has been successfully field tested. The results suggest that monitoring can sensitise surgeons to quality control, which can lead to a decrease in complication rates and improved visual outcomes.

Number of People Blind or Visually Impaired by Cataract Worldwide and in World Regions, 1990 to 2010.

PURPOSE To estimate prevalence and number of people visually impaired or blind due to cataract. METHODS Based on the Global Burden of Diseases Study 2010 and ongoing literature research, we examined how many people were affected by moderate to severe vision impairment (MSVI; presenting visual acuity <6/18, ≥3/60) and blindness (presenting visual acuity <3/60) due to cataract. RESULTS In 2010, of overall 32.4 million blind and 191 million vision impaired, 10.8 million people were blind and 35.1 million were visually impaired due to cataract. Cataract caused worldwide 33.4% of all blindness in 2010, and 18.4% of all MSVI. These figures were lower in the high-income regions (<15%) and higher (>40%) in South and Southeast Asia and Oceania. From 1990 to 2010, the number of blind or visually impaired due to cataract decreased by 11.4% and by 20.2%, respectively; the age-standardized global prevalence of cataract-related blindness and MSVI reduced by 46% and 50%, respectively, and the worldwide crude prevalence of cataract-related blindness and MSVI reduced by 32% and 39%, respectively. The percentage of global blindness and MSVI caused by cataract decreased from 38.6% to 33.4%, and from 25.6% to 18.4%, respectively. This decrease took place in almost all world regions, except East Sub-Saharan Africa. CONCLUSIONS In 2010, one in three blind people was blind due to cataract, and one of six visually impaired people was visually impaired due to cataract. Despite major improvements in terms of reduction of prevalence, cataract remains a major public health problem.

Rapid Assessment of Visual Impairment Due to Cataract and Cataract Surgical Services in Urban Argentina

Aim: To present results of a rapid assessment on visual impairment due to cataract and on cataract surgical services in the Northwestern districts of Buenos Aires, Argentina. These results will enable health managers to plan effective interventions in this area in line with VISION 2020. Methods: One hundred fifteen clusters of 40 persons of 50 years and older in each cluster (4600 eligible persons) were selected by systematic sampling from the Northwestern districts of Buenos Aires, Argentina. This area consists of 10 districts with a total population of 2,716,573 (2001 census), from whom 4302 persons were examined (coverage 93.5%). The visual acuity was measured with a tumbling E-chart and the lens status with distant direct ophthalmoscopy. Results: Cataract is the major cause of bilateral blindness (54.2%). The age and sex adjusted prevalence of bilateral cataract blindness (presenting VA < 20/400) in people of 50 years and older was 0.5% (95% CI: 0.4–0.8%), an estimated number of 2,985 persons. The cataract surgical coverage at this level was 70% for males and 78% for females. The prevalence of bilateral cataract and VA < 20/200 in persons of 50 years and older was 0.8% (95% CI: 0.6–1.1), an estimated 4,705 persons. In this last group, the surgical coverage was 66% (persons) and 57% (eyes). Of all operated eyes, 10% could not see 20/200. ‘Cannot afford’ (32%), ‘unaware of cataract’ (21%) and ‘contraindication for surgery’ (18%) were mentioned most as reason why surgery had not been done. Conclusion: The cataract problem is getting under control in this area. Coverage indicators are fairly high, and the outcome data better than in other studies. The cataract surgical rate could be raised further by awareness campaigns and by making cataract surgery more affordable.

New Systematic Review Methodology for Visual Impairment and Blindness for the 2010 Global Burden of Disease Study

Abstract Purpose: To describe a systematic review of population-based prevalence studies of visual impairment (VI) and blindness worldwide over the past 32 years that informs the Global Burden of Diseases, Injuries and Risk Factors Study. Methods: A systematic review (Stage 1) of medical literature from 1 January 1980 to 31 January 2012 identified indexed articles containing data on incidence, prevalence and causes of blindness and VI. Only cross-sectional population-based representative studies were selected from which to extract data for a database of age- and sex-specific data of prevalence of four distance and one near vision loss categories (presenting and best-corrected). Unpublished data and data from studies using rapid assessment methodology were later added (Stage 2). Results: Stage 1 identified 14,908 references, of which 204 articles met the inclusion criteria. Stage 2 added unpublished data from 44 rapid assessment studies and four other surveys. This resulted in a final dataset of 252 articles of 243 studies, of which 238 (98%) reported distance vision loss categories. A total of 37 studies of the final dataset reported prevalence of mild VI and four reported near VI. Conclusion: We report a comprehensive systematic review of over 30 years of VI/blindness studies. While there has been an increase in population-based studies conducted in the 2000s compared to previous decades, there is limited information from certain regions (eg, Central Africa and Central and Eastern Europe, and the Caribbean and Latin America), and younger age groups, and minimal data regarding prevalence of near vision and mild distance VI.

Global Vision Impairment and Blindness Due to Uncorrected Refractive Error, 1990-2010.

&NA; The purpose of this systematic review was to estimate worldwide the number of people with moderate and severe visual impairment (MSVI; presenting visual acuity <6/18, ≥3/60) or blindness (presenting visual acuity <3/60) due to uncorrected refractive error (URE), to estimate trends in prevalence from 1990 to 2010, and to analyze regional differences. The review focuses on uncorrected refractive error which is now the most common cause of avoidable visual impairment globally. &NA; The systematic review of 14,908 relevant manuscripts from 1990 to 2010 using Medline, Embase, and WHOLIS yielded 243 high-quality, population-based cross-sectional studies which informed a meta-analysis of trends by region. The results showed that in 2010, 6.8 million (95% confidence interval [CI]: 4.7–8.8 million) people were blind (7.9% increase from 1990) and 101.2 million (95% CI: 87.88–125.5 million) vision impaired due to URE (15% increase since 1990), while the global population increased by 30% (1990–2010). The all-age age-standardized prevalence of URE blindness decreased 33% from 0.2% (95% CI: 0.1–0.2%) in 1990 to 0.1% (95% CI: 0.1–0.1%) in 2010, whereas the prevalence of URE MSVI decreased 25% from 2.1% (95% CI: 1.6–2.4%) in 1990 to 1.5% (95% CI: 1.3–1.9%) in 2010. In 2010, URE contributed 20.9% (95% CI: 15.2–25.9%) of all blindness and 52.9% (95% CI: 47.2–57.3%) of all MSVI worldwide. The contribution of URE to all MSVI ranged from 44.2 to 48.1% in all regions except in South Asia which was at 65.4% (95% CI: 62–72%). &NA; We conclude that in 2010, uncorrected refractive error continues as the leading cause of vision impairment and the second leading cause of blindness worldwide, affecting a total of 108 million people or 1 in 90 persons.

Prevalence and Causes of Blindness in Children in Vietnam

OBJECTIVE To estimate the prevalence of blindness in children in Vietnam and to assess the major causes. DESIGN A population-based study sampled children from 16 provinces across Vietnam. The second study examined children attending all blind schools in Vietnam. PARTICIPANTS In 16 provinces, 28 800 children aged 0-15 were sampled. In 28 blind schools, 569 children aged 0-15 were examined. INTERVENTION In children not seeing well according to the parents, presenting visual acuity (PVA) was assessed. If PVA was <3/60 in one or both eyes, the child was examined by an ophthalmologist. All children in blind schools were examined by a pediatric ophthalmologist. MAIN OUTCOME MEASURES Blindness was defined as PVA <3/60 in the better eye. Causes of visual loss were classified using the World Health Organization classification. RESULTS In the population-based study, 22 children had a PVA <3/60 in the better eye, a prevalence of 7.6/10 000 children (95% confidence interval [CI], 4.9-11.8/10 000). Fourteen children had a pinhole visual acuity <3/60 in the better eye, a prevalence of 4.9/10 000 (95% CI, 2.8-8.4/10 000). An estimated 16 400 (95% CI, 10 500-25 300), children were blind from all causes, with 36.4% from uncorrected refractive errors. In the blind schools, 411 children had a PVA <3/60 in the better eye and 55.5% were male. Conditions of the retina (24.6%) and cornea (24.0%) predominated. Retinopathy of prematurity (ROP) caused blindness in 32.6% of children younger than 10 years, but in only 6% of older children. The converse was true for corneal scarring and phthisis (14.0% and 27.3%, respectively). All other causes were similar between age groups (53.5% and 66.7%, respectively). More than half of all causes were avoidable. CONCLUSIONS Vietnam is developing very rapidly, and this is impacting health indices. The mortality rate of those younger than 5 years declined from 65/100 live births in 1980 to 14/100 in 2008. The findings of this study show these changes, because the childhood blindness prevalence was relatively low, and the causes show improved control of measles and vitamin A deficiency, as well as increased services for premature babies. Eye care services for children should now focus on refractive errors, cataract, and control of ROP.