Abstract
Purpose:
To monitor macular pigment (MP) distribution profiles over periods of more than a decade in order to assess the long-term stability of MP optical density values at different retinal locations.
Methods:
Multiple MP spatial distribution profiles were obtained using a motion photometer in 4 healthy subjects (A-D) monitored over periods of 15.6, 14.7, 11.7 and 10.7 years respectively. A square wave grating (460nm and 580nm) was moved at constant horizontal velocity (26 deg/sec and/or 37 deg/sec) within 2 circular fields (radius 0.45° and 1.1°) and 11 annular segments (maximum radius 7.5°). The radiance of the 580nm stimulus was adjusted to minimize the perceived motion. Optical density (OD) was computed at each location relative to the most eccentric area from log (Rref/R), where Rref is the mean radiance setting for the most eccentric locations and R is the radiance setting at any location. The shape of the mean spatial distribution profiles for each of the 4 subjects (average of 46, 42, 12 and 10 profiles respectively) were characterised in detail.
Results:
Mean peak MPOD values obtained with a circular field (radius = 0.45°) were 0.89 (A), 0.76 (B), 0.45 (C) and 0.17 (D). The shapes of the mean MP profiles varied in a way representative of a normal population and were best described by the sum of 2 Gaussian functions, accounting for at least 99% of the variance. Linear regression through serial data points (circular field; radius 1.1°) gave gradients of 0.0093 (A), 0.0012 (B), -0.0003 (C) and -0.0024 (D) per year. Maximum gradients at 4 eccentricities at or between 0.82 and 2.31 degrees were 0.0075 (A), -0.0070 (B), 0.0026 (C) and 0.0049 (D) per year.
Conclusions:
Widely different MP distribution profiles in healthy subjects demonstrate a high degree of stability over periods of up to 15 years. The findings provide an assessment of normal stability that is pertinent to studies that aim to monitor MP in disease.
Keywords: 587 macular pigment •
444 carotenoids/carotenoid binding proteins •
461 clinical (human) or epidemiologic studies: natural history