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Jorge C. Gibert, Richard A. Bone, Anirbaan Mukherjee, John T. Landrum; Cumulative Light Distribution on the Human Retina: Implications for AMD. Invest. Ophthalmol. Vis. Sci. 2011;52(14):382.
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Because light exposure has been implicated in the etiology of age-related macular degeneration (AMD), the purpose of this study was to measure the cumulative light distribution on the human retina over extended periods. Since AMD damage is most pronounced in the macula, we hypothesized that light distributions would peak in the macular region.
A conventional head-mounted eye-tracker was used to record the subject's field of view with a video camera (30 frames/s), superimpose the gaze position (60 Hz), and simultaneously record pupil size. A test group was formed with fifteen naïve subjects who were divided into three age groups (10-20, 21-34, 39-65). A group of five subjects, who were familiar with the study, were assigned to a control group. In phase 1, subjects viewed 3 photographic images projected on a screen; in phase 2, they observed a PowerPoint consisting of 78 images; in phase 3, they were seated before a computer monitor and allowed to perform arbitrary computer tasks; in phase 4 the subjects viewed a video projected on a screen; in phase 5, they moved freely around the lab and exterior of the building. The control group was specifically instructed to gaze at bright features in the field of view and, in a second test, at dark features. All participants in the test group were allowed to gaze freely. Using the subject’s gaze coordinates within each movie frame, and the corresponding pupil diameter, we were able to calculate the cumulative light distribution over 5 minutes periods on a ~20o(H)x14o(V) area of the retina centered on the fovea.
Relative retinal light distribution maps were obtained for all 20 subjects. The data were quantified by plotting the relative intensity of light versus retinal position. As expected for the control group, cumulative retinal light distributions peaked and dipped in the fovea when the subjects gazed at bright or dark features respectively in the field of view. The distributions maps obtained from the test group showed a strong tendency to peak in the macula in phase 3, a slight tendency in phases 4 and 5 but no tendency in phases 1 and 2. However, it should be noted that these distribution maps were somewhat compressed owing to the limited dynamic range and automatic aperture feature of the video camera. No significant differences were observed between age groups.
Although specific tasks, such as working in front of a computer monitor, appear to expose the retina to a higher illuminance in the macular region, which could be a risk factor for AMD, we have not consistently found a similar result under general viewing conditions.
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