Genetic Studies of Macular Pigment

Abstract

One of the major functions suggested for macular pigment is to protect the retina. However, a tenfold variation in pigment level is observed in the general population, which cannot be explained by other factors, such as age, sex, race, eye or skin colour (Bone and Sparrock, 1971 Vision Research 11 1057 – 1064). We aim to examine the role of genetic factors in this variation. In our first experiments (Alexander and Moreland, 1996 Perception 25 Supplement, 105) we used colour matching to examine pigment levels in 23 local families. The highest correlation was seen for the father/child relationship where a linear regression accounted for 25% of the variance (p<0.01); no significant relationship was observed for mother/child, grandparent/grandchild, or, as expected, for the control parent/parent plot.

These families, and a few new ones, have been retested by a motion photometry paradigm, with a foveal 2 deg field and an extrafoveal annular field at 5 deg eccentricity. In the tests, a grating of alternating bars (460 nm and 580 nm) moves horizontally across the field at 14 Hz. The subject adjusts the luminance of the 580 nm bars for minimum perceived motion. The difference in setting between the two fields is used to measure the subject's pigment level. Analysis of preliminary data shows no significant correlation for any of the relationships but further analysis is in progress.