Abstract
Purpose: :
Recent work has suggested that macular pigment density (MPD) exists in two patterns of distribution – the classic Gaussian pattern and a bimodal, or annular, pattern. Here we compare and characterize the MPD distribution of normal and AMD subjects as well as primary relatives of AMD subjects (PRAMD).
Methods: :
117 Normal, 52 PRAMD, and 27 AMD subjects participated in this study. MPD was measured with free viewing heterochromatic flicker photometry (HFP) using test stimuli covering 10–minutes, 30–minutes, 1–degree, and 2–degrees of retinal eccentricity. Subjects also completed a nutritional questionnaire for analysis. MPD was categorized into two subgroups: classical group with MPD at 10–min > 30–min > 1–deg > 2–deg; annular group with MPD at 10–min < 30–min > 1–deg > 2–deg.
Results: :
24% of Normal, 38% of PRAMD, and 44% of AMD subjects had annular MPD distributions. There was a small, non–significant trend for MPD to increase with increasing age. Subjects over the age of 50 showed an increase in daily lutein intake through diet and supplementation with increasing age. This trend in lutein intake was significant for subjects older than 50 that had the classic MPD distribution. There were no significant intergroup differences in MPD at any of the four test loci. Subjects in the annular subgroup had higher daily intake of lutein in their diet. Age for the annular subgroup subjects was greater than the classic subjects among Normal and PRAMD subjects. However, AMD subjects with the annular pattern were on average younger than those with the classic MPD distribution.
Conclusions: :
There appear to be two patterns of MPD distribution: a classic, Gaussian MPD distribution and an annular MPD distribution were the central macular pigment is depressed. The annular pattern is present in 24% of normal subjects, 38% of PRAMD subjects, and 44% of AMD subjects. The higher percentage of PRAMD subjects with the annular pattern compared to normal subjects suggests a connection between the annular pattern and progression to AMD. Lutein consumption does not appear to affect this higher percentage, or it might actually be masking a higher percentage of PRAMD individuals at risk. The higher lutein intake of AMD and PRAMD subjects might account for the absence of a difference between their MPD profiles and that of their Normal counterparts. Overall, age does not appear to correlate with MPD, but in Normal and PRAMD subjects age appears to correlate with whether or not an individual has the annular pattern.
Keywords: macular pigment • carotenoids/carotenoid binding proteins • antioxidants