Influence of Macular Pigmentation on Acuity and Visibility

University Of Georgia Research Foundation Inc, Athens GA

Investigators

Abstract

The central portion of the human retina contains a yellow pigment (called macular pigment, MP) that is derived from dietary intake of the carotenoids lutein and zeaxanthin. There are two main hypotheses that attempt to explain the function of these pigments in the human eye. The "protection hypothesis" proposes that MP protects the sensitive retinal cells that line the back of the eye from damage due to oxygen and light. The "acuity hypothesis" proposes that MP improves visual resolution by absorbing short-wave (blue) light, which is easily scattered and poorly focused. This latter hypothesis was proposed over a century ago and has not been empirically verified. This grant tests this longstanding hypothesis and a new hypothesis regarding the role of MP in vision called the "visibility hypothesis." The visibility hypothesis is based on the idea that MP may improve vision through the atmosphere by preferentially absorbing blue haze (the short-wave component of natural sunlight that produces a veiling luminance when viewing objects at a distance). The acuity and visibility hypotheses are largely based on the idea that it is the short-wave (blue) portion of white sunlight light that degrades visual performance and that MP, by filtering this light before it is processed by the retinal photoreceptors, would improve vision. The investigators will test whether MP improves visibility and acuity using two experimental designs. In the first, the investigators will select subjects with a range of MP densities (filtering nearly all of the blue light or almost none of it) and test their visual performance using stimuli that are either degraded or not degraded by blue light. For the second set of studies, the investigators will pre-select individuals with very low MP and then use an artificial filter designed to mimic MP in order to test the effects on visual performance. These studies represent an important first step in determining the influence of dietary carotenoids on human vision.