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WILLIAM W. DAWSON, WARREN L. HERRON; Retinal Illumination During Indirect Ophthalmoscopy: Subsequent Dark Adaptation. Invest. Ophthalmol. Vis. Sci. 1970;9(2):89-96.
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Basal measures of the curve of dark adaptation were made during a 5 day period for the eyes of four visually normal subjects. At the end of this measurement period, one retina of each individual was thoroughly examined, quadrant by quadrant, by standard indirect ophthalmoscopy and the fundus picture drawn. The maximum illumination available from the ophthalmoscope was used in all examinations. Dark adaptation curves were plotted at increasing intervals after completion of the examination and the basal control and experimental eye results were examined for changes in the facility of adaptation. Analysis of variance of the data showed that there were no significant differences in the levels of dark adaptation achieved 50 minutes after the onset of darkness. However, inspection of summary graphs revealed that consistent differences between the experimental and control eye existed during the first eight minutes of dark adaptation. Statistical analysis on that period showed that the average experimental eye required more light for a threshold judgment during early dark adaptation than the control eye. High variability reduced the level of confidence (p ≅ 0.1). Radiometric and photometric calibration of the indirect ophthalmoscope illuminator indicated that approximately 90 per cent of its energy output was in the infra-red and contributed nothing to the visualization of the fundus.
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