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1.  The Nakuru eye disease cohort study: methodology & rationale 
BMC Ophthalmology  2014;14:60.
Background
No longitudinal data from population-based studies of eye disease in sub-Saharan-Africa are available. A population-based survey was undertaken in 2007/08 to estimate the prevalence and determinants of blindness and low vision in Nakuru district, Kenya. This survey formed the baseline to a six-year prospective cohort study to estimate the incidence and progression of eye disease in this population.
Methods/Design
A nationally representative sample of persons aged 50 years and above were selected between January 2007 and November 2008 through probability proportionate to size sampling of clusters, with sampling of individuals within clusters through compact segment sampling. Selected participants underwent detailed ophthalmic examinations which included: visual acuity, autorefraction, visual fields, slit lamp assessment of the anterior and posterior segments, lens grading and fundus photography. In addition, anthropometric measures were taken and risk factors were assessed through structured interviews. Six years later (2013/2014) all subjects were invited for follow-up assessment, repeating the baseline examination methodology.
Discussion
The methodology will provide estimates of the progression of eye diseases and incidence of blindness, visual impairment, and eye diseases in an adult Kenyan population.
doi:10.1186/1471-2415-14-60
PMCID: PMC4024270  PMID: 24886366
Cohort study; Longitudinal; Eye disease; Africa; Kenya; Cataract; Glaucoma; Age related macular degeneration; Diabetic retinopathy; Refractive error; Incidence; Progression
2.  The Long Term Impact of Cataract Surgery on Quality of Life, Activities and Poverty: Results from a Six Year Longitudinal Study in Bangladesh and the Philippines 
PLoS ONE  2014;9(4):e94140.
Background
Cataract surgery has been shown to improve quality of life and household economy in the short term. However, it is unclear whether these benefits are sustained over time. This study aims to assess the six year impact of cataract surgery on health related quality of life (HRQoL), daily activities and economic poverty in Bangladesh and The Philippines.
Methods and Findings
This was a longitudinal study. At baseline people aged ≥50 years with visual impairment due to cataract (‘cases’) and age-, sex-matched controls without visual impairment were interviewed about vision specific and generic HRQoL, daily activities and economic indicators (household per capita expenditure, assets and self-rated wealth). Cases were offered free or subsidised cataract surgery. Cases and controls were re-interviewed approximately one and six years later. At baseline across the two countries there were 455 cases and 443 controls. Fifty percent of cases attended for surgery. Response rates at six years were 47% for operated cases and 53% for controls. At baseline cases had poorer health and vision related QoL, were less likely to undertake productive activities, more likely to receive assistance with activities and were poorer compared to controls (p<0.05). One year after surgery there were significant increases in HRQoL, participation and time spent in productive activities and per capita expenditure and reduction in assistance with activities so that the operated cases were similar to controls. These increases were still evident after six years with the exception that time spent on productive activities decreased among both cases and controls.
Conclusion
Cataract causing visual loss is associated with reduced HRQoL and economic poverty among older adults in low-income countries. Cataract surgery improves the HRQoL of the individual and economy of the household. The findings of this study suggest these benefits are sustained in the long term.
doi:10.1371/journal.pone.0094140
PMCID: PMC3991652  PMID: 24747192
3.  Prevalence of Age-Related Macular Degeneration in Nakuru, Kenya: A Cross-Sectional Population-Based Study 
PLoS Medicine  2013;10(2):e1001393.
Using digital retinal photography and slit lamp examination in a population-based sample in the Nakuru District of Kenya, Andrew Bastawrous and colleagues determined the prevalence of age-related macular degeneration in adults 50 years and older.
Background
Diseases of the posterior segment of the eye, including age-related macular degeneration (AMD), have recently been recognised as the leading or second leading cause of blindness in several African countries. However, prevalence of AMD alone has not been assessed. We hypothesized that AMD is an important cause of visual impairment among elderly people in Nakuru, Kenya, and therefore sought to assess the prevalence and predictors of AMD in a diverse adult Kenyan population.
Methods and Findings
In a population-based cross-sectional survey in the Nakuru District of Kenya, 100 clusters of 50 people 50 y of age or older were selected by probability-proportional-to-size sampling between 26 January 2007 and 11 November 2008. Households within clusters were selected through compact segment sampling.
All participants underwent a standardised interview and comprehensive eye examination, including dilated slit lamp examination by an ophthalmologist and digital retinal photography. Images were graded for the presence and severity of AMD lesions following a modified version of the International Classification and Grading System for Age-Related Maculopathy. Comparison was made between slit lamp biomicroscopy (SLB) and photographic grading.
Of 4,381 participants, fundus photographs were gradable for 3,304 persons (75.4%), and SLB was completed for 4,312 (98%). Early and late AMD prevalence were 11.2% and 1.2%, respectively, among participants graded on images. Prevalence of AMD by SLB was 6.7% and 0.7% for early and late AMD, respectively. SLB underdiagnosed AMD relative to photographic grading by a factor of 1.7.
After controlling for age, women had a higher prevalence of early AMD than men (odds ratio 1.5; 95% CI, 1.2–1.9). Overall prevalence rose significantly with each decade of age. We estimate that, in Kenya, 283,900 to 362,800 people 50 y and older have early AMD and 25,200 to 50,500 have late AMD, based on population estimates in 2007.
Conclusions
AMD is an important cause of visual impairment and blindness in Kenya. Greater availability of low vision services and ophthalmologist training in diagnosis and treatment of AMD would be appropriate next steps.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Worldwide, 39 million people are blind, and 246 million people (mainly living in developing countries) have moderate or severe visual impairment. The third leading global cause of blindness (after cataracts and glaucoma) is age-related macular degeneration (AMD). This group of conditions is characterized by lesions in the macular (central) region of the retina, the tissue at the back of the eye that converts light into electrical messages and sends them to the brain. AMD, which affects older people, destroys the sharp central vision that is needed for reading or driving, leaving only dim, blurred images or a black hole at the center of vision. AMD can be diagnosed by examining digital photographs of the retina or by examining the retina directly using a special magnifying lens (slit lamp biomicroscopy). There is no cure for AMD, although injections into the eye of certain drugs, such as bevacizumab, that block the activity of vascular endothelial growth factor can slow the rate of vision loss caused by some forms of AMD.
Why Was This Study Done?
Most investigations of the prevalence (the proportion of a population with a disease) of AMD and of risk factors for AMD have studied people with European or Asian ancestry. Very little is known about AMD in African populations, and the data that are available mainly come from African populations living outside Africa. It is important to know whether AMD is an important cause of visual impairment and blindness in Africa, so that informed decisions can be made about the need for AMD programs in African countries. In this cross-sectional population-based study, the researchers investigate the prevalence of AMD among people aged 50 years or older living in Nakuru District (an ethnically diverse region of Kenya) and look for predictors of AMD in this population. In a cross-sectional population-based study, researchers observe a representative subset of a population at a single time point.
What Did the Researchers Do and Find?
The researchers randomly selected 100 clusters of 50 people aged 50 years or older for their study. Between January 2007 and November 2008, study participants had a comprehensive eye examination and completed a standardized interview that included questions about their age, gender, other demographic details, medical history, and exposure to possible risk factors for AMD. Based on digital retinal images, the prevalences of early and late AMD among the study population were 11.2% and 1.2%, respectively. The prevalences of early and late AMD judged by slit lamp biomicroscopy were 6.7% and 0.7%, respectively. After controlling for age, women had a higher prevalence of both early and late AMD than men. The overall prevalence of AMD rose with age: compared to the youngest age group, the oldest age group had a three-fold higher risk of developing late AMD. Of the people with any grade of AMD, 25.6% had some visual impairment and 2.5% were blind. Overall, 9.9% of the blindness seen in the study was attributable to AMD.
What Do These Findings Mean?
These findings identify AMD as an important cause of visual impairment and blindness in Nakuru District, Kenya. Extrapolation of these findings to the whole of Kenya suggests that 283,900 to 362,800 Kenyans had early AMD and 25,200 to 50,500 had late AMD in 2007. The accuracy of these findings is limited by the inability to obtain digital retinal images from all the participants (often because of electricity failures) and by other aspects of the study design. Moreover, because the methodology used in this study differed from some other studies of AMD, the prevalence of AMD reported here cannot be compared directly to those found in other studies. Nevertheless, these findings have several important implications. In particular, although recent evidence suggests that bevacizumab is likely to be both effective and affordable in Africa, the infrastructure required to deliver an adequate AMD service is currently prohibitively expensive in most African countries. Thus, these findings suggest that it is essential that research is undertaken to support the development of AMD treatment programs that are affordable and deliverable in Africa, and that low vision resources are provided for individuals with vision impairment.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001393.
The US National Eye Institute provides detailed information about age-related macular degeneration
The UK National Health Service Choices website also provides information about age-related macular degeneration, including personal stories about the condition
The UK Royal National Institute of Blind People has information on age-related macular degeneration, including a video of a person describing their experiences of the condition
AMD Alliance International provides written and audio information in several languages about age-related macular degeneration, including a large selection of personal stories; the Macular Degeneration Partnership also provides information about age-related macular degeneration, including a simulation of the condition
MedlinePlus has links to additional resources about age-related macular degeneration (in English and Spanish)
doi:10.1371/journal.pmed.1001393
PMCID: PMC3576379  PMID: 23431274
4.  Balancing the books 
Community Eye Health  2013;26(83):41-43.
PMCID: PMC3864050  PMID: 24421569
5.  Does Cataract Surgery Alleviate Poverty? Evidence from a Multi-Centre Intervention Study Conducted in Kenya, the Philippines and Bangladesh 
PLoS ONE  2010;5(11):e15431.
Background
Poverty and blindness are believed to be intimately linked, but empirical data supporting this purported relationship are sparse. The objective of this study is to assess whether there is a reduction in poverty after cataract surgery among visually impaired cases.
Methodology/Principal Findings
A multi-centre intervention study was conducted in three countries (Kenya, Philippines, Bangladesh). Poverty data (household per capita expenditure – PCE, asset ownership and self-rated wealth) were collected from cases aged ≥50 years who were visually impaired due to cataract (visual acuity<6/24 in the better eye) and age-sex matched controls with normal vision. Cases were offered free/subsidised cataract surgery. Approximately one year later participants were re-interviewed about poverty. 466 cases and 436 controls were examined at both baseline and follow-up (Follow up rate: 78% for cases, 81% for controls), of which 263 cases had undergone cataract surgery (“operated cases”). At baseline, operated cases were poorer compared to controls in terms of PCE (Kenya: $22 versus £35 p = 0.02, Bangladesh: $16 vs $24 p = 0.004, Philippines: $24 vs 32 p = 0.0007), assets and self-rated wealth. By follow-up PCE had increased significantly among operated cases in each of the three settings to the level of controls (Kenya: $30 versus £36 p = 0.49, Bangladesh: $23 vs $23 p = 0.20, Philippines: $45 vs $36 p = 0.68). There were smaller increases in self-rated wealth and no changes in assets. Changes in PCE were apparent in different socio-demographic and ocular groups. The largest PCE increases were apparent among the cases that were poorest at baseline.
Conclusions/Significance
This study showed that cataract surgery can contribute to poverty alleviation, particularly among the most vulnerable members of society. This study highlights the need for increased provision of cataract surgery to poor people and shows that a focus on blindness may help to alleviate poverty and achieve the Millennium Development Goals.
doi:10.1371/journal.pone.0015431
PMCID: PMC2976760  PMID: 21085697
6.  Urbanization, ethnicity and cardiovascular risk in a population in transition in Nakuru, Kenya: a population-based survey 
BMC Public Health  2010;10:569.
Background
Cardiovascular disease (CVD) is the leading cause of death among older people in Africa. This study aimed to investigate the relationship of urbanization and ethnicity with CVD risk markers in Kenya.
Methods
A cross-sectional population-based survey was carried out in Nakuru Kenya in 2007-2008. 100 clusters of 50 people aged ≥50 years were selected by probability proportionate to size sampling. Households within clusters were selected through compact segment sampling. Participants were interviewed by nurses to collect socio-demographic and lifestyle information. Nurses measured blood pressure, height, weight and waist and hip circumference. A random finger-prick blood sample was taken to measure glucose and cholesterol levels.
Hypertension was defined as systolic blood pressure (SBP) ≥140 mm Hg, or diastolic blood pressure (DBP) ≥90 mm Hg or current use of antihypertensive medication; Diabetes as reported current medication or diet control for diabetes or random blood glucose level ≥11.1 mmol/L; High cholesterol as random blood cholesterol level ≥5.2 mmol/L; and Obesity as Body Mass Index (BMI)≥30 kg/m2.
Results
5010 eligible subjects were selected, of whom 4396 (88%) were examined. There was a high prevalence of hypertension (50.1%, 47.5-52.6%), obesity (13.0%, 11.7-14.5%), diabetes (6.6%, 5.6-7.7%) and high cholesterol (21.1%, 18.6-23.9). Hypertension, diabetes and obesity were more common in urban compared to rural groups and the elevated prevalence generally persisted after adjustment for socio-demographic, lifestyle, obesity and cardiovascular risk markers. There was also a higher prevalence of hypertension, obesity, diabetes and high cholesterol among Kikuyus compared to Kalenjins, even after multivariate adjustment. CVD risk markers were clustered both across the district and within individuals. Few people received treatment for hypertension (15%), while the majority of cases with diabetes received treatment (68%).
Conclusions
CVD risk markers are common in Kenya, particularly in urban areas. Exploring differences in CVD risk markers between ethnic groups may help to elucidate the epidemiology of these conditions.
doi:10.1186/1471-2458-10-569
PMCID: PMC2956724  PMID: 20860807
7.  The key informant method: a novel means of ascertaining blind children in Bangladesh 
Background
Most information on the causes of blindness has come from examining children in special education. To obtain a more representative population‐based sample of children, a novel method was developed for ascertaining severe visually impaired (SVI) or blind (BL) children by training local volunteers to act as key informants (KIs).
Objective
To compare the demography and cause of blindness in children recruited by KIs with other ascertainment methods.
Method
Children with SVI/BL were recruited in all 64 districts of Bangladesh. Three sources for case ascertainment were utilised: schools for the blind (SpEdu), community‐based rehabilitation (CBR) programmes and KIs. All data were recorded using the standard WHO/PBL Eye Examination Record.
Results
1935 children were recruited. Approximately 800 KIs were trained. The majority of the children were recruited by the KIs (64.3%). Children recruited by KIs were more likely to be female (odds ratio (OR) 1.6, p<0.001), of pre‐school age (OR 14.1, p<0.001), from rural areas (OR 5.9, p<0.001), be multiply impaired (OR 3.1, p = 0.005) and be suffering from treatable eye diseases (OR 1.3, p = 0.005) when compared with those in SpEdu. Overall a child with an avoidable causes of SVI/BL had 40% (adjusted CI 1.1 to 1.7, p = 0.015) and 30% (CI 1.0 to 1.7, p = 0.033) higher odds of being ascertained using the KIs compared with SpEdu and CBR methods, respectively.
Conclusion
Using this innovative approach has resulted in one of the largest studies of SVI/BL children to date. The findings indicate that KIs can recruit large numbers of children quickly, and that the children they recruit are more likely to be representative of all blind children in the community.
doi:10.1136/bjo.2006.108027
PMCID: PMC1954788  PMID: 17431019
8.  Cataract visual impairment and quality of life in a Kenyan population 
Aims
To evaluate the World Health Organization Prevention of Blindness and Deafness 20‐item Visual Functioning Questionnaire (WHO/PBD VF20), a vision‐related quality of life scale, and to describe the relationship between cataract visual impairment and vision‐ and generic health‐related quality of life, in people ⩾50 years of age in Nakuru district, Kenya.
Methods
The WHO/PBD VF20 was pilot tested and modified. 196 patients with visual impairment from cataract and 128 population‐based controls without visual impairment from cataract were identified through a district‐wide survey. Additional cases were identified through case finding. Vision‐ and health‐related quality of life were assessed using the WHO/PBD VF20 scale and EuroQol generic health index (European Quality of Life Questionnaire (EQ‐5D)), respectively. WHO/PBD VF20 was evaluated using standard psychometric tests, including factor analysis to determine item grouping for summary scores.
Results
The modified WHO/PBD VF20 demonstrated good psychometric properties. Two subscales (general functioning and psychosocial) and one overall eyesight‐rating item were appropriate for these data. Increased severity of visual impairment in cases was associated with worsening general functioning, psychosocial and overall eyesight scores (p for trend <0.001). Cases were more likely to report problems with EQ‐5D descriptive dimensions than controls (p<0.001), and, among cases, increased severity of visual impairment was associated with worsening self‐rated health score.
Conclusion
The modified WHO/PBD VF20 is a valid and reliable scale to assess vision‐related quality of life associated with cataract visual impairment in this Kenyan population. The association between health‐related quality of life and visual impairment reflects the wider implications of cataract for health and well‐being, beyond visual acuity alone.
doi:10.1136/bjo.2006.110973
PMCID: PMC1955630  PMID: 17272387
9.  The Impact of Cataract Surgery on Activities and Time-Use: Results from a Longitudinal Study in Kenya, Bangladesh and the Philippines 
PLoS ONE  2010;5(6):e10913.
Background
Cataract is the leading cause of blindness in the world, and blindness from cataract is particularly common in low-income countries. The aim of this study is to explore the impact of cataract surgery on daily activities and time-use in Kenya, Bangladesh and the Philippines.
Methods/Principal Findings
A multi-centre intervention study was conducted in three countries. Time-use data were collected through interview from cases aged ≥50 years with visually impairing cataract (VA <6/24) and age- and gender-matched controls with normal vision (VA≥6/18). Cases were offered free/subsidized cataract surgery. Approximately one year later participants were re-interviewed about time-use. At baseline across the three countries there were 651 cases and 571 controls. Fifty-five percent of cases accepted surgery. Response rate at follow up was 84% (303 out of 361) for operated cases, and 80% (459 out of 571) for controls. At baseline, cases were less likely to carry out and spent less time on productive activities (paid and non-paid work) and spent more time in “inactivity” compared to controls. Approximately one year after cataract surgery, operated cases were more likely to undertake productive activities compared to baseline (Kenya from 55% to 88%; Bangladesh 60% to 95% and Philippines 81% to 94%, p<0.001) and mean time spent on productive activities increased by one-two hours in each setting (p<0.001). Time spent in “inactivity” in Kenya and Bangladesh decreased by approximately two hours (p<0.001). Frequency of reported assistance with activities was more than halved in each setting (p<0.001).
Conclusions/Significance
The empirical evidence provided by this study of increased time spent on productive activities, reduced time in inactivity and reduced assistance following cataract surgery among older adults in low-income settings has positive implications for well-being and inclusion, and supports arguments of economic benefit at the household level from cataract surgery.
doi:10.1371/journal.pone.0010913
PMCID: PMC2879361  PMID: 20531957
10.  Outcomes of cataract surgery in Pakistan: results from The Pakistan National Blindness and Visual Impairment Survey 
Aim
To evaluate the outcomes of cataract surgery in Pakistan.
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.
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 (15.4%) eyes: 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 with 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.
doi:10.1136/bjo.2006.106724
PMCID: PMC1994747  PMID: 17151060
11.  Rapid assessment of avoidable blindness in Negros Island and Antique District, Philippines 
The British Journal of Ophthalmology  2007;91(12):1588-1592.
Objectives
To conduct rapid assessments of avoidable blindness to estimate the magnitude and causes of blindness in people aged ⩾50 years in Negros Island and Antique district, Philippines.
Methods
Clusters of 50 people aged ⩾50 years were sampled with probability proportionate to size. Households within clusters were selected through compact segment sampling. Visual acuity (VA) was measured with a tumbling “E” chart. Ophthalmologists examined people with VA<6/18 in either eye.
Results
In Negros, 2774 of 3649 enumerated subjects were examined (76.0%) and 3177 of 3842 enumerated subjects in Antique (82.7%). The prevalence of blindness (presenting VA<3/60 in better eye) was 2.6% (95% CI = 2.0 to 3.2%) in Negros and 3.0% (2.4 to 3.6%) in Antique. The leading cause of blindness was untreated cataract, and was refractive error for visual impairment (VA<6/18 to ⩾6/60). Most of the cases of blindness (67% in Negros, 82% in Antique) and visual impairment (94% in Negros, 95% in Antique) were avoidable (ie, operated and unoperated cataract, refractive error and corneal scar). In Negros, 23% of eyes had a poor outcome after cataract surgery, and 13% in Antique.
Conclusions
The prevalence of blindness in two areas in the Philippines was relatively low. Since most cases were avoidable, further reductions are possible.
doi:10.1136/bjo.2007.119123
PMCID: PMC2095536  PMID: 17567662
12.  Is quality affordable? 
Community Eye Health  2008;21(68):53-55.
PMCID: PMC2643032  PMID: 19287542
13.  A Case-Control Study to Assess the Relationship between Poverty and Visual Impairment from Cataract in Kenya, the Philippines, and Bangladesh 
PLoS Medicine  2008;5(12):e244.
Background
The link between poverty and health is central to the Millennium Development Goals (MDGs). Poverty can be both a cause and consequence of poor health, but there are few epidemiological studies exploring this complex relationship. The aim of this study was to examine the association between visual impairment from cataract and poverty in adults in Kenya, Bangladesh, and the Philippines.
Methods and Findings
A population-based case–control study was conducted in three countries during 2005–2006. Cases were persons aged 50 y or older and visually impaired due to cataract (visual acuity < 6/24 in the better eye). Controls were persons age- and sex-matched to the case participants with normal vision selected from the same cluster. Household expenditure was assessed through the collection of detailed consumption data, and asset ownership and self-rated wealth were also measured. In total, 596 cases and 535 controls were included in these analyses (Kenya 142 cases, 75 controls; Bangladesh 216 cases, 279 controls; Philippines 238 cases, 180 controls). Case participants were more likely to be in the lowest quartile of per capita expenditure (PCE) compared to controls in Kenya (odds ratio = 2.3, 95% confidence interval 0.9–5.5), Bangladesh (1.9, 1.1–3.2), and the Philippines (3.1, 1.7–5.7), and there was significant dose–response relationship across quartiles of PCE. These associations persisted after adjustment for self-rated health and social support indicators. A similar pattern was observed for the relationship between cataract visual impairment with asset ownership and self-rated wealth. There was no consistent pattern of association between PCE and level of visual impairment due to cataract, sex, or age among the three countries.
Conclusions
Our data show that people with visual impairment due to cataract were poorer than those with normal sight in all three low-income countries studied. The MDGs are committed to the eradication of extreme poverty and provision of health care to poor people, and this study highlights the need for increased provision of cataract surgery to poor people, as they are particularly vulnerable to visual impairment from cataract.
Hannah Kuper and colleagues report a population-based case-control study conducted in three countries that found an association between poverty and visual impairment from cataract.
Editors' Summary
Background.
Globally, about 45 million people are blind. As with many other conditions, avoidable blindness (preventable or curable blindness) is a particular problem for people in developing countries—90% of blind people live in poor regions of the world. Although various infections and disorders can cause blindness, cataract is the most common cause. In cataract, which is responsible for half of all cases of blindness in the world, the lens of the eye gradually becomes cloudy. Because the lens focuses light to produce clear, sharp images, as cataract develops, vision becomes increasingly foggy or fuzzy, colors become less intense, and the ability to see shapes against a background declines. Eventually, vision may be lost completely. Cataract can be treated with an inexpensive, simple operation in which the cloudy lens is surgically removed and an artificial lens is inserted into the eye to restore vision. In developed countries, this operation is common and easily accessible but many poor countries lack the resources to provide the operation to everyone who needs it. In addition, blind people often cannot afford to travel to the hospitals where the operation, which also may come with a fee, is done.
Why Was This Study Done?
Because blindness may reduce earning potential, many experts believe that poverty and blindness (and, more generally, poor health) are inextricably linked. People become ill more often in poor countries than in wealthy countries because they have insufficient food, live in substandard housing, and have limited access to health care, education, water, and sanitation. Once they are ill, their ability to earn money may be reduced, which increases their personal poverty and slows the economic development of the whole country. Because of this potential link between health and poverty, improvements in health are at the heart of the United Nations Millennium Development Goals, a set of eight goals established in 2000 with the primary aim of reducing world poverty. However, few studies have actually investigated the complex relationship between poverty and health. Here, the researchers investigate the association between visual impairment from cataract and poverty among adults living in three low-income countries.
What Did the Researchers Do and Find?
The researchers identified nearly 600 people aged 50 y or more with severe cataract-induced visual impairment (“cases”) primarily through a survey of the population in Kenya, Bangladesh, and the Philippines. They matched each case to a normally sighted (“control”) person of similar age and sex living nearby. They then assessed a proxy for the income level, measured as “per capita expenditure” (PCE), of all the study participants (people with cataracts and controls) by collecting information about what their households consumed. The participants' housing conditions and other assets and their self-rated wealth were also measured. In all three countries, cases were more likely to be in the lowest quarter (quartile) of the range of PCEs for that country than controls. In the Philippines, for example, people with cataract-affected vision were three times more likely than normally sighted controls to have a PCE in the lowest quartile than in the highest quartile. The risk of cataract-related visual impairment increased as PCE decreased in all three countries. Similarly, severe cataract-induced visual impairment was more common in those who owned fewer assets and those with lower self-rated wealth. However, there was no consistent association between PCE and the level of cataract-induced visual impairment.
What Do These Findings Mean?
These findings show that there is an association between visual impairment caused by cataract and poverty in Kenya, Bangladesh, and the Philippines. However, because the financial circumstances of the people in this study were assessed after cataracts had impaired their sight, this study does not prove that poverty is a cause of visual impairment. A causal connection between poverty and cataract can only be shown by determining the PCEs of normally sighted people and following them for several years to see who develops cataract. Nevertheless, by confirming an association between poverty and blindness, these findings highlight the need for increased provision of cataract surgery to poor people, particularly since cataract surgery has the potential to improve the quality of life for many people in developing countries at a relatively low cost.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050244.
This study is further discussed in a PLoS Medicine Perspective by Susan Lewallen
The MedlinePlus encyclopedia contains a page on cataract, and MedlinePlus also provides a list of links to further information about cataract (in English and Spanish)
VISION 2020, a global initiative for the elimination of avoidable blindness launched by the World Health Organization and the International Agency for the Prevention of Blindness, provides information in several languages about many causes of blindness, including cataract. It also has an article available for download on blindness, poverty, and development
Information is available from the World Health Organization on health and the Millennium Development Goals (in English, French, and Spanish)
The International Centre for Eye Health carries out research and education activities to improve eye health and eliminate avoidable blindness with a focus on populations with low incomes
doi:10.1371/journal.pmed.0050244
PMCID: PMC2602716  PMID: 19090614
15.  A National Survey of Musculoskeletal Impairment in Rwanda: Prevalence, Causes and Service Implications 
PLoS ONE  2008;3(7):e2851.
Background
Accurate information on the prevalence and causes of musculoskeletal impairment (MSI) is lacking in low income countries. We present a new survey methodology that is based on sound epidemiological principles and is linked to the World Health Organisation's International Classification of Functioning.
Methods
Clusters were selected with probability proportionate to size. Households were selected within clusters through compact segment sampling. 105 clusters of 80 people (all ages) were included. All participants were screened for MSI by a physiotherapist and medical assistant. Possible cases plus a random sample of 10% of non-MSI cases were examined further to ascertain diagnosis, aetiology, quality of life, and treatment needs.
Findings
6757 of 8368 enumerated individuals (80.8%) were screened. There were 352 cases, giving an overall prevalence for MSI of 5.2%. (95% CI 4.5–5.9) The prevalence of MSI increased with age and was similar in men and women. Extrapolating these estimates, there are approximately 488,000 MSI diagnoses in Rwanda. Only 8.2% of MSI cases were severe, while the majority were moderate (43.7%) or mild (46.3%). Diagnostic categories comprised 11.5% congenital, 31.3% trauma, 3.8% infection, 9.0% neurological, and 44.4% non-traumatic non infective acquired. The most common individual diagnoses were joint disease (13.3%), angular limb deformity (9.7%) and fracture mal- and non-union (7.2%). 96% of all cases required further treatment.
Interpretation
This survey demonstrates a large burden of MSI in Rwanda, which is mostly untreated. The survey methodology will be useful in other low income countries, to assist with planning services and monitoring trends.
doi:10.1371/journal.pone.0002851
PMCID: PMC2483936  PMID: 18682849
16.  Impact of Mass Distribution of Azithromycin on the Antibiotic Susceptibilities of Ocular Chlamydia trachomatis 
Antimicrobial Agents and Chemotherapy  2005;49(11):4804-4806.
In a community of Tanzania where trachoma is endemic, we cultured conjunctival swabs from all residents who had active trachoma and were PCR positive for ocular Chlamydia trachomatis, both before (43 isolates) and 2 months after (9 isolates) mass antibiotic treatment. No clinically or programmatically significant increase in azithromycin or tetracycline resistance was observed.
doi:10.1128/AAC.49.11.4804-4806.2005
PMCID: PMC1280160  PMID: 16251338
17.  Red eye: the role of primary care 
Community Eye Health  2005;18(53):69.
PMCID: PMC1705665  PMID: 17491744
18.  Diagnosis and Assessment of Trachoma 
Clinical Microbiology Reviews  2004;17(4):982-1011.
Trachoma is caused by Chlamydia trachomatis. Clinical grading with the WHO simplified system can be highly repeatable provided graders are adequately trained and standardized. At the community level, rapid assessments are useful for confirming the absence of trachoma but do not determine the magnitude of the problem in communities where trachoma is present. New rapid assessment protocols incorporating techniques for obtaining representative population samples (without census preparation) may give better estimates of the prevalence of clinical trachoma. Clinical findings do not necessarily indicate the presence or absence of C. trachomatis infection, particularly as disease prevalence falls. The prevalence of ocular C. trachomatis infection (at the community level) is important because it is infection that is targeted when antibiotics are distributed in trachoma control campaigns. Methods to estimate infection prevalence are required. While culture is a sensitive test for the presence of viable organisms and nucleic acid amplification tests are sensitive and specific tools for the presence of chlamydial nucleic acids, the commercial assays presently available are all too expensive, too complex, or too unreliable for use in national programs. There is an urgent need for a rapid, reliable test for C. trachomatis to assist in measuring progress towards the elimination of trachoma.
doi:10.1128/CMR.17.4.982-1011.2004
PMCID: PMC523557  PMID: 15489358
19.  VISION 2020: THE CATARACT CHALLENGE 
Community Eye Health  2000;13(34):17-19.
PMCID: PMC1705965  PMID: 17491949
20.  Optics & Refraction 
Community Eye Health  2000;13(33):8.
PMCID: PMC1705958  PMID: 17491945
22.  How Can Blind Children Be Helped? 
Community Eye Health  1998;11(27):33-34.
PMCID: PMC1706063  PMID: 17492035
24.  Blindness in the developing world 
Images
PMCID: PMC504724  PMID: 8123628

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