Antioxidant role in cataract prevention challenged
medwireNews: Antioxidant supplements do not reduce the need for age-related cataract surgery or prevent vision loss, suggest results from the Age-Related Eye Disease Study 2 (AREDS2).
The findings, published in JAMA Ophthalmology, show no significant difference in the outcome of patients randomly assigned to take daily doses of lutein/zeaxanthin 10 mg/2 mg (n=787), omega-3 long-chain polyunsaturated fatty acids 1 g (PUFAs, n=803), combined treatment (n=794), or placebo (n=775).
The participants, aged 50 to 85 years, were all at risk for age-related macular degeneration and the four treatment groups had comparable baseline cataract status, explain Emily Chew (National Eye Institute, Bethesda, Maryland, USA) and co-authors.
Serum analysis confirmed that median lutein levels were higher at year 1, 3, and 5 of the study than at baseline in the patients given the antioxidant combination, whereas controls had no change in concentrations.
Overall, 1389 (23%) of the 6027 study eyes required cataract surgery during a median of 4.7 years of follow-up. The 5-year rate of progression to cataract surgery was 24% regardless of whether patients used lutein/zeaxanthin, nor was there a significant difference between patients who were given PUFAs and those who were not.
In all, 30% of patients developed cataract and 25% developed a severe cataract but the rate of these outcomes did not significantly differ between patients given antioxidants and those who were not.
Supplements also had no effect on the likelihood of moderate or greater vision loss in the patients or the risk for clinically significant serious adverse effects.
"While observational studies have suggested that higher dietary intake or higher blood levels of lutein and zeaxanthin may have a protective effect on the development of cataract, this randomized, placebo-controlled trial did not find an effect of supplementation with lutein/zeaxanthin on cataract surgery, cortical or [posterior subcapsular cataract] lens opacity progression, or vision loss," Chew et al write.
However, the researchers note that the average participant was aged 72 years at baseline and antioxidants may have been too little or too late to protect against early-stage cataracts at baseline that had no visible opacities.
Furthermore, patients accepted into the AREDS2 study were better educated and better nourished than the general population, with higher dietary levels of lutein and zeaxanthin and multivitamin use.
The authors therefore caution: "Whether supplementation would be beneficial for less well-nourished populations requires further study."
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Lynda Williams, Senior medwireNews Reporter