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Loss of cone function in age-related maculopathy
Joanna A Phipps1, Robyn H Guymer, Algis J Vingrys
1Department of Optometry and Vision Sciences, University of Melbourne, Victoria, Australia.
Purpose:
To evaluate cone visual function of subjects with age-related maculopathy (ARM).
Methods:
Cone thresholds in 16 patients with ARM and 14 age-matched control subjects were compared. All subjects had visual acuity of 6/12 or better in the studied eye. A range of contrast thresholds were measured to evaluate diverse aspects of cone visual function under steady state conditions (spatiotemporal, color and luminance, and photopic sensitivity) or after bleaching (adaptation dynamics).
Results:
ARM produced a diffuse loss across all cone steady state visual functions in 31% to 44% of subjects. The adaptation time constant of cone recovery was significantly prolonged in most (69%) ARM eyes. A cross-correlational analysis found adaptational kinetics to be independent of other steady state losses, with cone photopigment regeneration being the most affected visual function in ARM (chi(2) = 4.03, P < 0.05).
Conclusions:
The results show that cone-adaptational kinetics are affected in ARM more so than are steady state thresholds. Given that cone recovery is easy to examine in a clinical setting, this test may provide a useful index of photopic function in patients with ARM.