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R. A. Bone, J. C. Gibert, J. T. Landrum; Cumulative Light Distribution on the Human Retina Under Natural Viewing Conditions. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2261.
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Since light has been implicated in the etiology of age-related macular degeneration (AMD), the purpose of our study was to measure the cumulative light distribution on the human retina over extended periods. Our hypothesis was that light distributions would peak in the macula where AMD damage is most pronounced.
A head-mounted eye-tracker captured the subject's field of view with a video camera (60 frames/s), superimposed the gaze position, and continuously recorded pupil size. Fifteen subjects, ages 18-65, participated. Five, who were familiar with the study, were assigned to a control group; 10, who were naïve, formed a test group. In phase 1, subjects viewed a sequence of photographic images projected on a screen. In phase 2, they were seated before a computer monitor and allowed to browse the Internet, and in phase 3, they moved freely around the lab and exterior of the building. As a check, the control group was specifically instructed to gaze at bright features in the field of view and, in a second test, at dark features. The rest of the participants were allowed to gaze freely. Based on the subject’s gaze position within each movie frame, and the corresponding pupil diameter, we calculated the cumulative light distribution over 5 to 15 min periods on a ~20o(H)×14o(V) area of the retina centered on the fovea.
Relative retinal light distributions maps were obtained for all 15 subjects. The data were quantified by plotting the relative intensity of light versus retinal position. 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 light distributions obtained from the test group in phase 2, but not in phases 1 and 3, showed a tendency to peak in the macula.
At this stage of our investigation, we have not been able to confirm our hypothesis that the macula receives more light than the periphery under general viewing conditions. However, specific tasks, such as working in front of a computer monitor, appear to expose the retina to a higher illuminance in the macular region, and this could have implications as far as development of AMD is concerned.
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