Health News and Research

Antioxidant Supplementation Helps Reduce Cataract Incidence

Cataracts are a clouding of the lens in the eye that affects vision and one of the leading causes of irreversible blindness, along with age-related macular degeneration. By age 80, more than half of all Americans either have a cataract or have had a cataract surgically removed.

Supplementing with vitamin E and superoxide dismutase and following a diet low on the glycemic index may help maintain eye health. A new study has found that including beta-carotene and vitamin C may also help maintain eye health.

In the study, nearly 300 patients from the U.S. and U.K. were given either an antioxidant supplement that provided a daily dose of 18 mg of beta-carotene, 750 mg of vitamin C and 600 mg of vitamin E or placebo. The patients were followed for two to four years (231 were followed for two years; 158 for three years and 36 (12%) for four years). Cataract severity, in the form of increasing opacity (cloudiness) of the lens was the main outcome measure of the study and was measured using serial digital retroillumination imagery of the lens.

While there were no statistically significant differences between patients in regards to lens opacity at the beginning of the study, researchers found that the longer the study lasted, the greater the differences between the supplement and placebo groups. With a small positive treatment effect after two years of treatment, this increased after three years to a positive effect and was apparent in both the U.S. and the U.K. groups. For the U.S. group, however, the positive effect was even greater after three years and was thought to be related to the base diet of those in the U.S. versus the U.K.

The researchers concluded, “Daily use of the afore-mentioned micronutrients for three years produced a small deceleration in progression of ARC.”

Abstract

CONTEXT: Funding surgery worldwide for age-related cataract (ARC), a leading cause of blindness, is a huge economic burden. Non-surgical means of slowing ARC progression could benefit patients and reduce this burden. OBJECTIVE: To determine if a mixture of oral antioxidant micronutrients [mg/day] (beta-carotene [18], vitamin C [750], and vitamin E [600]) would modify progression of ARC. DESIGN: REACT was a multi-centered, prospective, double-masked, randomized, placebo-controlled, 3-year trial. SETTING: Consecutive adult American and English outpatients with early ARC were recruited. PATIENTS: Four-hundred-and-forty-five patients were eligible; 297 were randomized; 231 (78%) were followed for two years; 158 (53%) were followed for three years; 36 (12%) were followed for four years. Twelve patients died during the trial (9 on vitamins; 3 on placebo (p = 0.07)). There were no serious safety issues. INTERVENTION: After a three-month placebo run-in, patients were randomized by clinical center to the vitamin or placebo groups and followed every four months. MAIN OUTCOME MEASURE: Cataract severity was documented with serial digital retroillumination imagery of the lens; progression was quantified by image analysis assessing increased area of opacity. This measure of area, 'increase % pixels opaque' (IPO), was the main outcome measure. RESULTS: There were no statistically significant differences between the treatment groups at baseline. The characteristics of dropouts and the mean follow-up times by treatment group were the same. After two years of treatment, there was a small positive treatment effect in U.S. patients (p = 0.0001); after three years a positive effect was apparent (p = 0.048) in both the U.S. and the U.K. groups. The positive effect in the U.S. group was even greater after three years: (IPO = 0.389 (vitamin) vs. IPO = 2.517 (placebo); p = 0.0001). There was no statistically significant benefit of treatment in the U.K. group. In spite of nearly perfect randomization into treatment groups, the U.S. and U.K. cohorts differed significantly. CONCLUSION: Daily use of the afore-mentioned micronutrients for three years produced a small deceleration in progression of ARC.
 

Source:

Chylack, L.T., Jr., et al., The Roche European American Cataract Trial (REACT): a randomized clinical trial to investigate the efficacy of an oral antioxidant micronutrient mixture to slow progression of age-related cataract. Ophthalmic Epidemiol, 2002 Feb. 9(1): p. 49-80.
 

Key concepts: Antioxidants, carotenoids, beta-carotene, vitamin C, cataracts