THE RELATIONSHIP BETWEEN CATARACT AND CLIMATIC DROPLET KERATOPATHY INMONGOLIA

This study evaluated the association between cataract the commonest si ngle blinding disorder worldwide, and climatic droplet keratopathy whi ch was taken as an indicator of high exposure to ultraviolet sunlight. A sample of 4344 persons from rural Mongolia (1991-99) provided 8634 eyes for analysis of the relationship between cataract and climatic dr oplet keratopathy. Right and left eyes were combined (paired into matc hed sets), and analysed using a random-effects regression model. The r esults indicated an inverse association between cataract and climatic droplet keratopathy in person aged 55 years or older, whereby eyes wit h more advanced climatic droplet keratopathy had lower prevalence of c ataract (age-adjusted odds ratio 0.53, p = 0.047). In the younger grou p of persons aged 40-54 years, the reverse was found, whereby cataract prevalence was higher in eyes that have climatic droplet keratopathy (age-adjusted odds ratio 13.19, p = 0.046). However, only a small prop ortion (4%) of all the cataracts occurred in this younger age stratum where the prevalence of cataract was 0.5%, compared to prevalence of 1 7% in eyes of persons aged 55 years or older. These findings cast furt her doubts upon the current thesis that lifetime exposure to high leve ls of ultraviolet sunlight is a major cause of cataract in developing countries.