Juan Carlos Silva

Elimination of Neglected Diseases in Latin America and the Caribbean: A Mapping of Selected Diseases

In Latin America and the Caribbean, around 195 million people live in poverty, a situation that increases the burden of some infectious diseases. Neglected diseases, in particular, are often restricted to poor, marginalized sections of the population. Tools exist to combat these diseases, making it imperative to work towards their elimination. In 2009, the Pan American Health Organization (PAHO) received a mandate to support the countries in the Region in eliminating neglected diseases and other poverty-related infections. The objective of this study is to analyze the presence of selected diseases using geo-processing techniques. Five diseases with information available at the first sub-national level (states) were mapped, showing the presence of the disease (“hotspots”) and overlap of diseases (“major hotspots”). In the 45 countries/territories (approximately 570 states) of the Region, there is: lymphatic filariasis in four countries (29 states), onchocerciasis in six countries (25 states), schistosomiasis in four countries (39 states), trachoma in three countries (29 states), and human rabies transmitted by dogs in ten countries (20 states). Of the 108 states with one or more of the selected diseases, 36 states present the diseases in overlapping areas (“major hotspots”). Additional information about soil-transmitted helminths was included. The analysis suggests a majority of the selected diseases are not widespread and can be considered part of an unfinished agenda with elimination as a goal. Integrated plans and a comprehensive approach, ensuring access to existing diagnostic and treatment methods, and establishing a multi-sectoral agenda that addresses social determinants, including access to adequate water and sanitation, are required. Future studies can include additional diseases, socio-economic and environmental variables.

Causes of Blindness and Visual Impairment in Latin America

We review what is known in each country of the Latin American region with regards to blindness and visual impairment and make some comparisons to Hispanic populations in the United States. Prevalence of blindness varied from 1.1% in Argentina to 4.1% in Guatemala in people 50 years of age and older, with the major cause being cataract. Diabetic retinopathy and glaucoma are starting to make serious inroads, although epidemiological data are limited, and age-related macular degeneration is now a concern in some populations. Infectious diseases such as trachoma and onchocerciasis are quickly diminishing. Although progress has been made, retinopathy of prematurity remains the major cause of childhood blindness. If VISION 2020 is to succeed, many more epidemiological studies will be needed to set priorities, although some can be of the Rapid Assessment of Avoidable Blindness design. Developing the infrastructure for screening and treatment of ophthalmic disease in Latin America continues to be a challenge.

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 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.

Ocular Histopathologic Characteristics of Cobalamin C Type Vitamin B12 Defect With Methylmalonic Aciduria and Homocystinuria

The eyes of a 22-month-old girl with the cobalamin C complementation type of combined methylmalonic aciduria and homocystinuria were studied with light and electron microscopy. We observed vacuolization of the iris pigment epithelium, loss of photoreceptors in the central 3.3 mm of the macula, partial loss of the nerve fiber and ganglion cell layers between the fovea and optic disk, and partial optic atrophy. The sclera in the posterior pole was thickened with deposition of mucopolysaccharide. Electron microscopy showed inclusions containing fine granular material in conjunctival fibrocytes; corneal epithelium, keratocytes, and endothelial cells; iris pigment epithelium; ganglion cells; retinal pigment epithelium; and choroid and scleral fibrocytes. Enlarged mitochondria and clear vacuoles distended the corneal endothelial cells. We found evidence of possible lysosomal dysfunction and mucopolysaccharide storage, as well as a clinicopathologic correlation of the macular degeneration in this disease.

Prevalence and causes of vision loss in Latin America and the Caribbean: 1990–2010

Objective To present regional estimates of the magnitude and temporal trends in the prevalence and causes of blindness and moderate/severe visual impairment (MSVI) in Latin America and the Caribbean (LAC). Methods A systematic review of cross-sectional population-representative data from published literature and unpublished studies was accessed and extracted to model the estimated prevalence of vision loss by region, country and globally, and the attributable cause fraction by region. Results In the LAC combined region, estimated all-age both-gender age-standardised prevalence of blindness halved from 0.8% (0.6 to 1.1) in 1990 to 0.4% (0.4 to 0.6) in 2010 and MSVI decreased from 4.3% (3.1 to 5.3) to 2.7% (2.2 to 3.4). In the Caribbean, estimated all-age both-gender age-standardised prevalence of blindness decreased from 0.6% (0.4 to 0.8) in 1990 to 0.5% (0.4 to 0.6) in 2010 and MSVI decreased from 3.3% (1.3 to 4.1) in 1990 to 2.9% (1.8 to 3.8). In the LAC regions combined, there was an estimated 2.3 million blind and 14.1 million with MSVI in 2010. In 2010, cataract continues to contribute the largest proportion of blindness, except in Southern Latin America where macular degeneration is most common. In 2010, uncorrected refractive error was the most common cause of MSVI. Conclusions While models suggest a decrease in age-standardised prevalence estimates, better data are needed to evaluate the disparities in the region. The increasing numbers of older people, coupled with the increase in vision loss associated with older age, will require further intervention to continue to reduce prevalence rates and to prevent a rise in absolute numbers of blind.

Cataract Surgery Rates in Latin America: A Four-Year Longitudinal Study of 19 Countries

Purpose: To collect cataract surgery rates data in 19 Latin American countries over a 4-year period as data published to date have been limited. Methods: Cataract surgery rates were obtained from National Society of Ophthalmology, National VISION 2020/Prevention of Blindness Committee and Ministry of Health representatives for each country for 2005 to 2008. Economic (gross national income per capita) and other data were collected from publicly available databases. Linear and power correlations between gross national incomes and cataract surgery rates were calculated. Results: Over the study period, most countries increased their cataract surgery rates, with the largest increases observed for Venezuela (186%), Nicaragua (183%), Costa Rica (100%), Uruguay (97%), and Peru (88%). Mean cataract surgery rates for 2005, 2006, 2007, and 2008 for the ensemble of countries were 1545, 1684, 1660, and 1822 per million population, respectively, with a growth over the study period of 17.9%, concurrent with an increase of 57 million (11.5%) in the population. A good correlation between cataract surgery rate and gross national income per capita was found (P < .001). Conclusions: Although progress is being made in the region, the cataract surgery rates represent only one parameter. When they are examined in the context of cataract surgical coverage it is clear that substantial proportions of bilaterally blind persons are still not receiving surgery.

Variation in cataract surgery needs in latin america.

OBJECTIVE To estimate and compare the incidence of operable cataract and the desired cataract surgery rates required to eliminate cataract-related visual impairment in several Latin American settings. METHODS We obtained raw data on age-specific cataract prevalence from standardized population-based surveys. We used the data in a previously described model to estimate the incidence of operable cataract at 11 sites in 10 countries across Latin America. Age-specific incidence rates were then multiplied by corresponding population data to calculate the desired cataract surgery rates needed to eliminate cataract-related visual impairment in eyes in each country. Age-standardized incidence was also calculated to explore potential non-age-related differences in incidence among the countries. RESULTS The desired cataract surgery rates ranged from 3441 to 8935 in the 11 sites. Much of the variation was owing to differing age structures, but there may be important variation in age-specific incidence rates as well. CONCLUSIONS Age structure has a major effect on the number of cataract surgeries needed in different countries of Latin America, and it is essential to consider this when planning cataract surgical services. Potential differences in non-age-related risk factors for cataract among different populations also deserve further study.

River blindness: An old disease on the brink of elimination and control

For decades, onchocerciasis (or river blindness) was one of the most common infectious causes of blindness in the world. Primarily an infection of Africa, with limited distribution in the new world, disease due to the nematode Onchocerca volvulus is rapidly diminishing as a result of large public health campaigns targeting at risk populations in Africa and the Americas. Existing and newly-developed treatment strategies offer the chance to eliminate onchocercal ocular morbidity in some parts of the world. This article reviews these treatment strategies, current clinical and epidemiologic aspects of onchocerciasis, and the next steps toward elimination.

Review of blindness and visual impairment in Paraguay: changes between 1999 and 2011.

Abstract Purpose: To report the prevalence and causes of blindness in people aged 50 years and older in Paraguay, and to compare these with the previous national survey in 1999, focusing on planning of future eye care activities. Methods: A rapid assessment of avoidable blindness (RAAB) was conducted in 2011. A total of 60 clusters of 50 residents aged 50 years and older were randomly selected and visited, and 2862 people were examined (95.4%). Survey data were analyzed with the RAAB software and compared with findings of a similar survey from 1999. Results: The prevalence of bilateral blindness in Paraguay was 1.0% (95% confidence interval, CI, 0.6–1.6) in 2011, significantly less than the 3.1% (95% CI 2.2–4.4) in 1999. Prevalence of bilateral cataract and cataract eyes had also reduced significantly for visual acuity, VA, <3/60, VA < 6/60 and VA < 6/18. Cataract surgical coverage in persons doubled to 90% for VA < 3/60, 78% for VA < 6/60 and 63% for VA < 6/18. Visual outcome after cataract surgery also improved to nearly the World Health Organization norm. Cataract was the main cause of blindness (43.8%), followed by severe visual impairment (40.5%). Uncorrected refractive errors were the main cause of moderate (78.0%) and the second cause of severe (18.9%) visual impairment. Conclusion: The reduction in blindness and visual impairment due to cataract in Paraguay between 1999 and 2011 was highly significant. Results and coverage of cataract surgical services improved substantially. The reported numbers of cataract operations may not have been complete as these do not seem to match the dramatic improvement in the cataract situation in Paraguay.