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Updated: Jun 19, 2026

Measuring the Behavioral Effects of Intraocular Scatter
Published on: February 18, 2021
THEORY AND MEASUREMENT OF VISUAL MECHANISMS : I. A VISUAL DISCRIMINOMETER. II. THRESHOLD STIMULUS INTENSITY AND
1Biological Laboratories, Harvard University, Cambridge.
Abstract:
Monocular threshold stimulus intensities (DeltaI(o), photons) were measured along the 0-180 degrees meridian of human retinae for three observers. The test image was small (= 0.08 degrees ) and of short duration (= 0.20 second). DeltaI(o) was found to decrease as the angular distance from the fovea was increased. Actual counts of the number of retinal elements per mm.(2) along the 0-180 degrees meridian (Østerberg) were compared with the obtained results. No direct correlation was found to exist between visual sensitivity and the number of retinal elements. Binocular threshold stimuli were also measured along the same meridian. The form of the function relating binocular visual sensitivity and retinal position was discovered to be essentially similar to that for monocular sensitivity, but is more symmetrical about the center of the fovea. The magnitude of the binocular measurement is in each case smaller than that of the monocular threshold stimulus intensity for the more sensitive eye. The ratio is statistically equal to 1.4 (a fact which suggests Piper's rule). These results are shown to be consistent with the hypothesis that the process critical for the eventuation of the threshold response is localized in the central nervous system. They are not consistent with the view that the quantitative properties of visual data are directly determined by properties of the peripheral retina.
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