Distribution of light on the retina over extended periods

Abstract

Purpose Implicated in the etiology of age‐related macular degeneration (AMD) is photooxidative damage. Our purpose was to measure light distribution on the retina integrated over extended periods. Our hypothesis was that such distributions would peak in the macula where AMD is most evident. Methods Using an eye‐tracker, the subject's field of view, gaze position and pupil size were continuously recorded. 5 subjects familiar with the study formed a control group; 10 naïve subjects formed a test group. In phase 1, subjects viewed photographic images projected on a screen. In phase 2, they were seated before a monitor and asked to perform typical computer tasks. In phase 3, they moved freely around the lab. The control group was asked to gaze at bright objects in the field of view and, in a second test, at dark objects. The test subjects were allowed to gaze freely. Based on the subject’s gaze position and pupil size over 5 to 15 min periods, the cumulative light distribution on the retina was calculated Results For the control group, retinal illuminance peaked or dipped in the fovea for the tests in which subjects gazed at bright or dark objects respectively, thereby validating the experimental procedure. The retinal illuminace obtained from the test group in phase 2, but not in phase 1, consistently peaked at the fovea. In phase 3, such peaking occurred in 2 subjects. Conclusion Our data indicate that there may be specific tasks (e.g. computer usage) that expose the macula to increased illuminance compared with the surrounding retina, and that there may be some individuals for whom this is true under general viewing conditions. In these cases, higher illuminance in the macular region could result in increased photooxidative damage with implications for development of AMD.