A study of eyes over a 10-year period has identified the progression of nuclear cataract can be attributed to genetic factors (35 per cent variance) and environmental factors (65 per cent), with dietary vitamin C providing significant protection.
Age-related cataract is the leading cause of blindness in the world, affecting approximately 20 million people.
Nuclear cataract data was available for 2,515 white female twins from the TwinsUK cohort, 2,054 of whom had completed a food frequency questionnaire within approximately two years of their eye examination. Of these, follow-up cataract measurements were available for 324 of the twins (151 monozygotic and 173 dizygotic twins) over the age of 60 years.
The study found that people with a higher vitamin C intake were associated with a 33 per cent risk reduction of cataract progression and had clearer lenses after 10 years than those with a lower vitamin C intake. Vitamin C has a protective effect on cataract progression by increasing the vitamin C available in the eye fluid, which helps stop the lens from oxidising and protects it from becoming cloudy.
Dietary manganese was also found to be protective against cross-sectional nuclear cataract, independent of vitamin C, however the authors noted that this could be due to a “type 1 error” and further studies would be required.
Although previous studies (Age-Related Eye Disease Study and the Blue Mountains Eye Study) have shown that vitamin C intake through both diet and supplements together resulted in a lower nuclear cataract incidence over 10 years, the authors wrote, “This was the first study, to our knowledge, to show that dietary vitamin C intake protects against progression of nuclear lens opacity”. They found “no statistically significant association between taking micronutrients in supplemental form and progression of nuclear cataract”.
The study was published online in March 2016.1
1. ‘Genetic and Dietary Factors Influencing the Progression of Nuclear Cataract’, available at: www.aaojournal.org/article/S0161-6420%2816%2900114-7/pdf [accessed 4 April 2016].