Abstract
Purpose: :
A number of recent studies have evaluated the relation between macular pigment density (MP) and several visual indices. These indices include visual sensitivity, glare disability, photostress, contrast thresholds, temporal function, and spatial vision tested under conditions designed to assess the effects of chromatic aberration (CA). However, many of these relations are not linear. In this study, we examined the idea that it is an actual deficiency of MP that is related to visual function loss and that MP levels greater than average are often superfluous. Specifically, we tested grating acuity at a number of frequencies under broad-band (influenced by CA) and short-wave deficient conditions.
Methods: :
20 young health subjects were tested. MPOD was measured using HFP. The CSF was evaluated using sinusoidal gratings presented at six spatial frequencies (2, 4, 8, 15, 22, and 43 cycles/degree) using broadband light (a xenon spectrum) or short-wave deficient light matched with respect to luminance. A criterion-free forced choice method was used to measure contrast sensitivity.
Results: :
MPOD ranged from 0.08 to 0.90 (for a 30’ radius stimulus). Contrast sensitivity measured with short-wave deficient (not absorbed by MP) and broad-band light (absorbed by MP) was similar at all frequencies except the highest (43 cycles/degree). For this frequency, MP was inversely related (p<0.05) to acuity thresholds.
Conclusions: :
A number of visual functions do appear to be influenced monotonically as a function of MP amount. Effects of MP on delimiting chromatic aberration, however, seem confined to the highest frequencies and are only evident for those subjects with the lowest MP levels.
Keywords: macular pigment • visual acuity