Abstract
Purpose: :
To systematically evaluate evidences from randomized controlled trials on the effectiveness of antioxidant supplements in preventing the development and slowing the progression of age related cataract.
Methods: :
Electronic databases such as the Cochrane Central Register of Controlled Trials, Medline in process via Ovid, Embase via Ovid, and CINAHL via EBSO were searched. We also explored the Google Scholar website, the website of the National Institute for Health Research, Google internet, and checked the reference list of retrieved reviews and included clinical trials. Only randomized controlled trials comparing antioxidant vitamins and mineral supplements taking alone or in combination to placebo or no antioxidant intervention in people with or without age related cataract were selected for inclusion. Data was analyzed using both qualitative and quantitative methods. Statistical pooling was undertaken using the fixed effect model for trials with low chi square and little variability between them.
Results: :
Eight trials with a total of 107874 participants met the inclusion criteria. The antioxidant investigated varied across trials, and not all the trials contributed to the Meta analysis of each antioxidant. Pooled results from single antioxidant comparison indicated that vitamin E had no significant effect on the development and progression of nuclear (RR, 0.95; 95% CI, 0.87-1.02; p = 0.18) and cortical (RR, 0.93; 95% 0.81 - 1.06; P = 0.24) age related cataract. Also, the result was not in favor of beta carotene except among current smokers (RR, 0.75; 95% CI, 0.60-0.94; p = 0.01). Broad spectrum antioxidant (Centrum) was effective only on nuclear age related cataract. The combined antioxidant comparison of riboflavin plus niacin versus no vitamins resulted in highly protective and significant effect (OR, 0.59; CI, 0.45 - 0.79; p = <0.001). However, other combination of any of the following: retinol, zinc, ascorbic acid, molybdenum, selenium, alpha-tocopherol, beta carotene from the Sperduto and AREDS trials yielded no effect on the development and deceleration of age related cataract.
Conclusions: :
While the impact on smoking related cataracts with beta carotene has been noted, additional randomized studies with larger enrollments are required to determine the impact of other supplements on various types of age related cataracts in relation to dosing, duration and onset of treatment.
Keywords: antioxidants • cataract • aging