Available data on blindness (update 1994)
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Biomedical subjects
Publications and source records attributed to R Pararajasegaram.
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Globally, it is estimated that there are 38 million persons who are blind. Moreover, a further 110 million people have low vision and are at great risk of becoming blind. The main causes of blindness and low vision are cataract, trachoma, glaucoma, onchocerciasis, and xerophthalmia; however, insufficient data on blindness from causes such as diabetic retinopathy and age-related macular degeneration preclude specific estimations of their global prevalence. The age-specific prevalences of the major causes of blindness that are related to age indicate that the trend will be for an increase in such blindness over the decades to come, unless energetic efforts are made to tackle these problems. More data collected through standardized methodologies, using internationally accepted (ICD-10) definitions, are needed. Data on the incidence of blindness due to common causes would be useful for calculating future trends more precisely.
World Health Organization (W.H.O.) carried out a survey recently. This survey consisted in a questionnaire to some of its Member States to try to define the importance and world distribution of trachoma. The answers which have been sent by ocular health advisers and/or persons in charge of national ophthalmological institutes showed a systemic lack of significant data to be used for planning or for epidemiological surveillance. Nevertheless, the analysis of this survey seems to lead to the conclusion that trachoma is not still the main cause of blindness in some countries who used to be famous because of an important endemicity. However, trachoma is still a real ocular health and public health problem in numerous other countries, mainly in rural areas and- or areas which are away from socio-sanitary development areas. To have a better quality concerning epidemiological data and to obtain an easier regularity in their collecting, W.H.O. Program for the Blindness Prevention proposed a simplified coding system of trachoma and its complications (S.S.C.T.C.). If this system was accepted by numerous countries it would allow: the use of a simple, reliable and cheap tool to collect epidemiological informations which would constitute an help to take decisions to be able to, give a second start to epidemiological surveillance of trachoma, to have a better idea of the localization of endemic centres of the disease and of this impact on population, to define the needs concerning collective and individual medical and surgical treatments.
This report presents the major findings of the Nepal Blindness Survey, the first nationwide epidemiological survey of blindness, which was conducted in 1979-80. The survey was designed to gather data that could be used to estimate the prevalence and causes of blindness in the country. Ancillary studies were conducted to obtain information on socioeconomic correlates and other risk factors of blinding conditions and patterns of health care utilization.The nationwide blindness prevalence rate is 0.84%. Cataract is the leading cause of blindness, accounting for over 80% of all avoidable blindness. Trachoma is the most prevalent blinding condition, affecting 6.5% of the population. Very few cases of childhood blindness were detected.The implications of the survey findings for programme planning, health manpower development, and health education are discussed.
The relationship between cataract prevalence, altitude, and sunlight hours was investigated in a large national probability sample survey of 105 sites in the Himalayan kingdom of Nepal, December 1980 through April 1981. Cataract of senile or unknown etiology was diagnosed by ophthalmologists in 873 of 30,565 full-time life-long residents of survey sites. Simultaneously, the altitude of sites was measured using a standard mountain altimeter. Seasonally adjusted average daily duration of sunlight exposure for each site was calculated by a method which took into account latitude and obstructions along the skyline. Age- and sex-standardized cataract prevalence was 2.7 times higher in sites at an altitude of 185 meters or less than in sites over 1000 meters. Cataract prevalence was negatively correlated with altitude (r = -0.533, p less than 0.0001). However, a positive correlation between cataract prevalence and sunlight was observed (r = 0.563, p less than 0.0001). Sites with an average of 12 hours of sunlight exposure had 3.8 times as much cataract as sites with an average of only seven hours of exposure. Sunlight was blocked from reaching certain high altitude sites by tall neighboring mountains.
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