Abstract
Purpose: :
To monitor macular pigment (MP) profiles over several years 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 in 4 healthy subjects (A - D) over periods of between 9 and 13 years using a motion photometer. Two subjects were additionally tested at monthly intervals over 2 years. 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 7.4°). 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.
Results: :
The shapes of MP profiles varied in a way representative of a normal population and were described by the sum of 2 Gaussian functions, accounting for more than 98% of the variance. Mean peak MPOD values ranged from approximately 0.16 to 0.87 and the lateral extent (OD=0.04) ranged from 1.2° to 4.4°. Linear regression through serial data points (2° circular field) measured over a period of 13 years gave gradients of 0.010 (A) and 0.008 (B) per year; over 9 years gradients were 0.005 (C) and -0.002 (D) per year. Gradients were lower at almost every other eccentric retinal location. The corresponding gradients for the monthly data taken over 2 years were 0.0003 (A) and -0.0002 (B) per year.
Conclusions: :
Widely different MP distribution profiles in healthy subjects demonstrate a high degree of short-term and long-term stability. The findings provide an assessment of normal stability that is pertinent to studies that aim to monitor MP in disease.
Keywords: macular pigment • carotenoids/carotenoid binding proteins • clinical (human) or epidemiologic studies: systems/equipment/techniques