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Cynthia Owsley, Gregory R. Jackson, Artur V. Cideciyan, Yijun Huang, Stuart L. Fine, Allen C. Ho, Maureen G. Maguire, Virginia Lolley, Samuel G. Jacobson; Psychophysical Evidence for Rod Vulnerability in Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2000;41(1):267-273.
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purpose. To determine whether there is rod system dysfunction in the central
retina of patients with age-related macular degeneration (AMD).
methods. Dark-adapted sensitivity (500-nm stimulus) and light-adapted
sensitivity (600 nm) were measured psychophysically at 52 loci in the
central 38° (diameter) of retina in 80 patients with AMD, and results
were compared with those from older adult normal controls. All
dark-adapted data were corrected for preretinal absorption.
results. Mean field dark-adapted sensitivity was significantly lower in AMD
patients as a group than in normal subjects. Within the AMD group were
subsets of patients with normal mean dark- and light-adapted
sensitivities; reduced dark-adapted sensitivities without detectable
light-adapted losses; both types of losses; and, least commonly, only
light-adapted losses. Regional retinal analyses of the dark-adapted
deficit indicated the greatest severity was 2° to 4° or
approximately 1 mm from the fovea, and the deficit decreased with
conclusions. These psychophysical results are consistent with histopathologic
findings of a selective vulnerability for parafoveal rod photoreceptors
in AMD. The different patterns of rod and cone system losses among
patients at similar clinical stages reinforces the notion that AMD is a
group of disorders with underlying heterogeneity of mechanism of visual
loss. Dark-adapted macula-wide testing may be a useful complement to
the more traditional outcome measures of fundus pathology and foveal
cone-based psychophysics in future AMD trials.
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