medwireNews: Macular pigmentation correlates with visual acuity in healthy individuals and people with early age-related macular degeneration (AMD), study results indicate.
The findings raise the possibility of improving retinal function through the use of drugs that promote macular pigmentation, say the study authors writing in Acta Ophthalmologica.
Macular pigment is a yellow substance comprised of two dietary carotenoids, lutein and zeaxanthin, that builds up in the retina and is most dense at the center of the macula. The pigment selectively filters out short-wave light and also has antioxidant properties, leading researchers to hypothesize that it may protect against AMD.
In this study, María Puell (Complutense University, Madrid, Spain) and colleagues examined the relationship between macular pigment optical density (MPOD) and measures of visual function in 22 people with early AMD and 27 healthy age-matched control individuals.
MPOD was estimated at the fovea using the cathode ray tube-based Metropsis psychophysical vision test. The mean MPOD was 0.30 log units in healthy controls versus 0.27 log units in people with early AMD, a nonsignificant difference.
High-contrast and low-contrast visual acuity were also comparable between healthy patients and those with AMD, at 0.03 versus 0.06 logMAR for high-contrast and 0.24 versus 0.26 logMAR for low-contrast, respectively.
As none of these parameters differed between the groups, Puell's team undertook a regression analysis. This revealed statistically significant relationships between MPOD and high-contrast visual acuity, at an r-value of -0.47, and with low-contrast visual acuity, at an r-value of -0.46.
"Thus, as MPOD increased, visual acuity improved," explain Puell et al.
The researchers note that earlier studies have examined augmentation of MPOD through dietary supplementation with lutein and zeaxanthin and found that this intervention enhances visual function in people with AMD. The mechanisms whereby lutein supplementation affects retinal function have yet to be elucidated, however.
They conclude: "Further studies are required to address the relationship between macular pigment and visual function in AMD eyes with low baseline macular pigment levels.
"Specifically, we should try to determine the threshold MPOD level below which supplements known to increase macular pigment could be effective to improve vision."
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By Joanna Lyford, Senior medwireNews Reporter