Associations Among Cataract Prevalence, Sunlight Hours, and Altitude in the Himalayas1

Abstract

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.

A study to explore the risk factors for the early onset of cataract in India

“…Lens opacification has been linked to ocular exposure to UV radiation particularly UV B. 42 Few authors 43,44 found a positive correlation between cataract prevalence and duration of sunlight exposure. In the present study, PSC followed by nuclear cataract was documented in patients experiencing occupational exposure to sunlight.…”

“…Cataract has a multifactorial aetiology with genetic, 1 sociodemographic, 2 behavioral, and environmental factors 3,4 all being implicated. Although it is likely that these factors interact with each other, age is still the single most important risk factor for cataract.…”

“…[9][10][11] The search for modifiable risk factors that affect the occurrence of cataract has prompted investigators to explore possible links between cataract and diabetes, hypertension, body mass index, drug usage, severe dehydrational crises, gender, smoking, exposure to UV light, childbearing, and socioeconomic factors. [1][2][3][4][10][11][12][13][14][15][16][17][18] Very few studies have been undertaken to explore risk factors for presenile cataract and they indicate that nearly 50% of the participants were exposed to at least one known risk factor including trauma, intraocular inflammation, diabetes mellitus, and the use of steroids. [19][20][21] We believe that it is worth investigating presenile cataract in developing countries, as this group may be exposed to potentially modifiable risk factors.…”

Non-trachomatous corneal opacities in the Gambia—aetiology and visual burden

“…This trend of increased prevalence of nontrachomatous corneal opacity compared to trachomatous corneal opacity has also been demonstrated in other developing countries. [5][6][7] Non-trachomatous corneal opacity therefore warrants close attention from national eye care planners seeking to reverse this trend. Previous data concerning this type of disease in African populations are few.…”

Catatrac: a novel red light-emitting diode device for screening cataracts in the developing world

“…[11][12][13] Equipment such as slit lamps have been used, as well as more basic equipment such as torches, and  2.5 loupes. 8,14 The availability of an accurate and cheap screening tool that could be easily used by non-ophthalmologists would potentially be of great use in cataract detection.…”