Association of cataract and sun exposure in geographically diverse populations of India: the case study. first report of the ICMR-EYE SEE study group

Purpose: To determine the prevalence of cataract and its association with
sun exposure and other environmental risk factors in three different
geographically diverse populations of India. Design: Population based
cross sectional study during 2010-2016 Participants: People aged >
40 years residing in randomly sampled villages were enumerated (12021) and
9735 (81%) underwent ophthalmic evaluation from plains, hilly and coastal
regions (3595, 3231, 2909 respectively) Methods: A detailed
questionnaire-based interview about outdoor activity in present, past and
remote past, usage of sun protective measures, exposure to smoke, and
detailed ophthalmic examination including assessment of uncorrected and
best corrected visual acuity, measurement of intraocular pressure, slit
lamp examination, lens opacities categorization using LOCS III and
posterior segment evaluation was done. Lifetime effective sun exposure was
calculated using Melbourne formula and expressed as quantiles. These were
supplemented with physical environmental measurements. Main outcome
measures: Lifetime sun exposure hours, smoking, indoor kitchen smoke
exposure and their association with cataract and subtypes. Prevalence of
cataract calculated based on lens opacities or evidence of cataract
surgery. Results: Cataract was identified in 3231 (33.3%) participants.
Prevalence of cataract in males (32.3%) and females (34.1%) was similar.
Nuclear cataract was the commonest sub-type identified in 94.7% of
affected eyes. Sun exposure had a significant association with cataract
with odds ratio (OR) increasing from 1.6 (95% Confidence Intervals [CI]:
1.4, 1.9) in 3rd quantile, to 2.6 (CI: 2.2, 3.1) in 4th quantile and 9.4
(CI: 7.9, 11.2) in 5th quantile (p<0.0001). Cataract also showed a
significant association with smoking (OR: 1.4, CI: 1.2, 1.6) and indoor
kitchen smoke exposure (OR: 1.2, CI: 1.0-1.4). Nuclear cataract showed a
positive association with increasing sun exposure in 3rd (β coefficient
0.5, CI:0.2-0.7), 4th (β: 0.9, CI: 0.7-1.1) and 5th (β: 2.1, CI:1.8-2.4)
quantiles of sun exposure, smoking (β: 0.4, CI: 0.2-0.6) and indoor
kitchen smoke exposure (β: 0.3, CI: 01-0.5) while cortical cataract showed
a positive association with sun exposure only in 5th quantile (β: 2.6,
CI:1.0-4.2). Posterior subcapsular cataract was not associated with any of
the risk factors. Conclusion: Cataract is associated with increasing level
of sun exposure, smoking and exposure to indoor kitchen smoke.