Abstract
Purpose: :
Some of the most significant age-related changes within the visual system are related to neural processing speed. Aging and retinal disease strongly impact temporal vision as assessed by the temporal modulation transfer function (TMTF) (e.g., as much as 84% of patients with early AMD show central deficits in their TMTF; Phipps et al., 2004). The precise nature of these deficits is often prognostic. For example, although the higher frequency portions of the TMTF are strongly influenced by post-receptoral processes, the lower frequency portions are probably more impacted by changes within the retina itself. The protective hypothesis of macular pigment (MP) predicts two important effects on the TMTF: that the relation between MP and the TMTF is both age- and spatially dependent. If MP protects against loss that accrues with time, the relation should be more pronounced for older subjects as opposed to younger subjects showing little loss. Moreover, if MP protects as a filter/antioxidant, the relation should be most pronounced when the TMTF is measured in the fovea where MP density peaks.
Methods: :
To test these predictions, MP optical density is being assessed via heterochromatic flicker photometry, and TMTF are being measured psychophysically via a novel optical device for younger and older subjects in both the central and peripheral retina. To investigate the role of MP carotenoids on post-receptoral function, electroencephalographic data relating MP density and TMTF to steady-state visual evoked response potentials will also be presented.
Results: :
As a preliminary assessment of MP's relation to the overall TMTF, we measured the relation between MP and CFF thresholds in 135 subjects (aged 17-92 years). The relation between age and CFF (p<0.0001) and CFF and MP density (p<0.001) was strongly significant.
Conclusions: :
Our initial data suggest that MP is related to temporal vision. We are currently assessing the relation between MP and the entire TMTF. These results will be presented.
Keywords: macular pigment • temporal vision • aging: visual performance