Lutein and zeaxanthin are the only carotenoids that can filter the harmful blue light that damages eye cells, and must be dense enough in the macula of the eye to provide protection. Doctors measure this protection as “macular pigment optical density” or MPOD. In this study, 112 people with early age-related macular degeneration (AMD) took 10 mg of lutein with or without 10 mg of zeaxanthin per day, 20 mg of lutein alone per day, or a placebo. After two years, lutein alone or with zeaxanthin increased MPOD compared to placebo. Retinal function —a measure of vision—increased significantly in the central retina, where vision first deteriorates in AMD. A significant percentage of the population has early AMD, and most studies have focused only on late-stage AMD. Doctors said lutein and zeaxanthin may also increase MPOD and improve visual performance in healthy people without AMD. 

Reference: British Journal of Ophthalmology; September, 2014, Published Online.