Abstract
Purpose::
Macular pigment (MP) is composed of the two dietary carotenoids lutein (L) and zeaxanthin (Z). There is a high degree of inter-subject variability in terms of peak optical density, spatial profile, and lateral extent of MP, and it has been suggested that foveal architecture may play a role in this variability. The present study was designed to investigate the spatial profile of MP and its relationship with foveal architecture in 60 normal subjects.
Methods::
The spatial profile of MP optical density (MPOD) was measured psychophysically using heterochromatic flicker photometry (HFP). High-resolution macular thickness maps were obtained using optical coherence tomography (OCT). Dietary, lifestyle, and vision information was obtained from each volunteer by questionnaire.
Results::
The mean (± 1 SD) MPOD at 0.25o eccentricity was 0.49 (± 0.23) and at 0.5o eccentricity was 0.41 (± 0.21). A first-order decreasing exponential function described the averaged subjects’ MP profile well (r2 = 0.991). MPOD at 0.25o was unrelated to both minimum and central foveal thickness (r = 0.031, p = 0.813 and r = -0.076, p = 0.566, respectively). MPOD at 0.5o of eccentricity was also unrelated to both minimum and central foveal thickness (r = 0.122, p = 0.356 and r = -0.049, p = 0.711, respectively). There was a positive and significant relationship between foveal width and the averaged MPOD across the fovea (r = 0.406, p = 0.001).
Conclusions::
Foveal MPOD is positively and significantly related to foveal width, but is unrelated to foveal thickness. These results indicate that the spatial profile and overall density of MP across the fovea is directly related to an individual’s foveal width. This relationship could be mediated by the increased number of L & Z binding sites in those individuals with wider foveas. Further studies using novel techniques of retinal imaging such as the next generation of OCT, should facilitate further exploration of our findings.
Keywords: macular pigment • age-related macular degeneration • clinical research methodology