Silvio P Mariotti

Global data on visual impairment in the year 2002

This paper presents estimates of the prevalence of visual impairment and its causes in 2002, based on the best available evidence derived from recent studies. Estimates were determined from data on low vision and blindness as defined in the International statistical classification of diseases, injuries and causes of death, 10th revision. The number of people with visual impairment worldwide in 2002 was in excess of 161 million, of whom about 37 million were blind. The burden of visual impairment is not distributed uniformly throughout the world: the least developed regions carry the largest share. Visual impairment is also unequally distributed across age groups, being largely confined to adults 50 years of age and older. A distribution imbalance is also found with regard to gender throughout the world: females have a significantly higher risk of having visual impairment than males. Notwithstanding the progress in surgical intervention that has been made in many countries over the last few decades, cataract remains the leading cause of visual impairment in all regions of the world, except in the most developed countries. Other major causes of visual impairment are, in order of importance, glaucoma, age-related macular degeneration, diabetic retinopathy and trachoma.

Global estimates of visual impairment: 2010

Aim From the most recent data the magnitude of visual impairment and its causes in 2010 have been estimated, globally and by WHO region. The definitions of visual impairment are the current definitions of presenting vision in the International Classification of Diseases version 10. Methods A systematic review was conducted of published and unpublished surveys from 2000 to the present. For countries without data on visual impairment, estimates were based on newly developed imputation methods that took into account country economic status as proxy. Results Surveys from 39 countries satisfied the inclusion criteria for this study. Globally, the number of people of all ages visually impaired is estimated to be 285 million, of whom 39 million are blind, with uncertainties of 10–20%. People 50 years and older represent 65% and 82% of visually impaired and blind, respectively. The major causes of visual impairment are uncorrected refractive errors (43%) followed by cataract (33%); the first cause of blindness is cataract (51%). Conclusion This study indicates that visual impairment in 2010 is a major health issue that is unequally distributed among the WHO regions; the preventable causes are as high as 80% of the total global burden.

Global magnitude of visual impairment caused by uncorrected refractive errors in 2004

Estimates of the prevalence of visual impairment caused by uncorrected refractive errors in 2004 have been determined at regional and global levels for people aged 5 years and over from recent published and unpublished surveys. The estimates were based on the prevalence of visual acuity of less than 6/18 in the better eye with the currently available refractive correction that could be improved to equal to or better than 6/18 by refraction or pinhole. A total of 153 million people (range of uncertainty: 123 million to 184 million) are estimated to be visually impaired from uncorrected refractive errors, of whom eight million are blind. This cause of visual impairment has been overlooked in previous estimates that were based on best-corrected vision. Combined with the 161 million people visually impaired estimated in 2002 according to best-corrected vision, 314 million people are visually impaired from all causes: uncorrected refractive errors become the main cause of low vision and the second cause of blindness. Uncorrected refractive errors can hamper performance at school, reduce employability and productivity, and generally impair quality of life. Yet the correction of refractive errors with appropriate spectacles is among the most cost-effective interventions in eye health care. The results presented in this paper help to unearth a formerly hidden problem of public health dimensions and promote policy development and implementation, programmatic decision-making and corrective interventions, as well as stimulate research.

Trachoma: global magnitude of a preventable cause of blindness

Objectives: Trachoma is the leading cause of infectious blindness worldwide. It is known to be highly correlated with poverty, limited access to healthcare services and water. In 2003, the WHO estimated that 84 million people were suffering from active trachoma, and 7.6 million were severely visually impaired or blind as a result of trachoma: this study provides an updated estimate of the global prevalence of trachoma based on the most recent information available. Methods: A literature search of recent published and unpublished surveys in the 57 endemic countries was carried out: the result of surveys that used the WHO trachoma grading system and additional information from regional and country experts served as a basis to determine the prevalence of trachoma in each country. Results: Population-based surveys provided recent information for 42 out of 57 endemic countries. 40.6 million people are estimated to be suffering from active trachoma, and 8.2 million are estimated to have trichiasis. Conclusions: The current estimate of prevalence of trachoma is lower than the previous WHO estimates: this can be explained by the success in implementing control strategy, by more accurate data, as well as by socio-economic development in endemic countries.

The Global Trachoma Mapping Project: Methodology of a 34-Country Population-Based Study

ABSTRACT Purpose: To complete the baseline trachoma map worldwide by conducting population-based surveys in an estimated 1238 suspected endemic districts of 34 countries. Methods: A series of national and sub-national projects owned, managed and staffed by ministries of health, conduct house-to-house cluster random sample surveys in evaluation units, which generally correspond to “health district” size: populations of 100,000–250,000 people. In each evaluation unit, we invite all residents aged 1 year and older from h households in each of c clusters to be examined for clinical signs of trachoma, where h is the number of households that can be seen by 1 team in 1 day, and the product h × c is calculated to facilitate recruitment of 1019 children aged 1–9 years. In addition to individual-level demographic and clinical data, household-level water, sanitation and hygiene data are entered into the purpose-built LINKS application on Android smartphones, transmitted to the Cloud, and cleaned, analyzed and ministry-of-health-approved via a secure web-based portal. The main outcome measures are the evaluation unit-level prevalence of follicular trachoma in children aged 1–9 years, prevalence of trachomatous trichiasis in adults aged 15 + years, percentage of households using safe methods for disposal of human feces, and percentage of households with proximate access to water for personal hygiene purposes. Results: In the first year of fieldwork, 347 field teams commenced work in 21 projects in 7 countries. Conclusion: With an approach that is innovative in design and scale, we aim to complete baseline mapping of trachoma throughout the world in 2015.

Cost-effectiveness of trachoma control in seven world regions.

Background/aims: The fight against blinding trachoma is being addressed with an integrated strategy of surgery, antibiotics, hygiene promotion, and environmental improvement—the SAFE strategy, but its cost-effectiveness is largely unknown. This paper estimates the cost effectiveness of surgery and antibiotics in trachoma-endemic areas in seven world regions. Methods: A population model was applied to follow the lifelong impact on individuals receiving trachoma control. Intervention costs and effectiveness estimates were based on a combination of primary data collection and literature review.Results: Providing trichiasis surgery to 80% of those who need it would avert over 11 million DALYs per year globally, with cost effectiveness ranging from I

Preventive chemotherapy and the fight against neglected tropical diseases

13 to I

Response from Savioli and Colleagues from the Department of Neglected Tropical Diseases, World Health Organization

78 per DALY averted across regions. Mass antibiotic treatment of all children using azythromycin at prevailing market prices would avert more than 4 million DALYs per year globally with cost-effectiveness ranging between I

The Future of Eye Care in a Changing World: Call for Papers

9,000 and I

Mapping the global distribution of trachoma

65,000 per DALY averted. The intervention is only cost-effective if azythromycin is donated or becomes available at reduced prices. Mass treatment of all children with tetracycline and targeted treatment with azythromycin are not cost-effective.Conclusions: As individual components of the SAFE strategy, trichiasis surgery for trachoma is a cost-effective way of restoring sight in all epidemiological sub-regions considered, as is the use of azythromycin, if donated or at reduced prices. Large study uncertainties do not change study conclusions. The results should be interpreted in the context of the overall SAFE strategy to address issues of sustainability.