Capturing light and age-related changes in spatial vision H Gillespie-Gallery, E Konstantakopoulou, J L Barbur |
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Applied Vision Research Centre, City University London, United Kingdom
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| Capturing vision changes at low light levels can help separate the effects of normal aging of the retina and visual pathways from early stage disease. The limits of normal, age-related changes in monocular and binocular functional contrast sensitivity were measured from photopic to mesopic light levels. 95 participants, age 20 to 85 years were examined. Measurements of contrast sensitivity were made using a four-alternative, forced-choice procedure at the fovea (0°) and parafovea (±4°), along the horizontal meridian. Pupil size was measured continuously for screen luminances 34-0.12cd/m2. The Health of the Retina index (HRindex) was computed to capture the rate of decline in contrast sensitivity with decreasing light level. Participants were excluded if they exhibited signs of ocular disease, or performance outside normal limits for interocular differences or HRindex values. The HRindex showed greater decline and correlation with age at the parafovea (r2=-0.34) than the fovea (r2=-0.19), consistent with histological findings of rod loss and its link to age-related degenerative disease. 23% of clinically normal participants had HRindex values outside normal limits. Binocular summation of contrast signals declined with age, independently of interocular differences. The HRindex, interocular differences and binocular summation can be used to detect early-stage, sub-clinical disease. |
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