The relationship of the size of the surrounding field to visual acuity in the fovea.

Abstract

Among the numerous variables which determine the nature of the visual process one of the more recent to come under quantitative investigation has been the condition of the retina apart from the region the function of which is being directly measured. The growing interest in this field has had both a theoretical and a practical motivation. Approached from the view of illuminating engineering, the brightness distribution in the visual field is important in many aspects of modern life. This orientation has led chiefly to a study of the effects of glare sources in the field of view. On the other hand, attempts at theoretical formulation of the visual process have so far failed to be completely satisfactory, perhaps because none of them has adequately included the factor of the surrounding field. Even in the restricted field of the photosensory process, the most valuable formulation, that of Hecht ( 23), fails at more than one point to account for the data; and the importance of the omission from his equation of any term descriptive of the condition of the retina outside the area tested is 1 The writer is indebted to Professor Robert T. Ross and to Professor Walter R. Miles for guidance during the course of this experiment and for valuable criticisms and suggestions in the preparation of the manuscript.This work was submitted to the faculty of the Graduate School of Yale University in partial fulfillment of the requirements for the degree of Doctor of Philosophy.

Some factors in brightness discrimination.

“…The fact that synchronization of discharge, in the optic nerve, comparable to the impressed rhythm from intermittent stimulation, develops spontaneously (1) is also contributory evidence in favor of the optic nerve discharge pattern being in reality an intrinsic function of the neural apparatus of the retina. In such a case, the discharge would be quite similar in principle to the intrinsic rhythm of the motoneuron (16).…”

Stimulus Determinants of Dynamic Visual Acuity. II. Effects of Limiting the Target Surround.

“…When these variables are allowed to covary, their effects are compounded. Interactive effects have been demonstrated for target type and luminance (11, 18), luminance and retinal position (19), surround luminance and target luminance (12,13), and size and contrast (20)(21)(22)(23). Acuity performance is further affected by dynamic characteristics of stimulus-response interactions that occur as a *1!…”

Simultaneous contrast as a function of separation between test and inducing fields.

“…Variation of stimuli in the visual field while simultaneously investigating the effects of foveal stimulation is a common operation in experimental studies of simultaneous contrast (6,9,10,22,24) and brightness constancy (7), and has been shown to be a variable in studies on the absolute threshold (3,4,12), visual acuity (8,18), flicker (19), vernier acuity (10), intensity discrimination (21), and size constancy (17). In order to analyze such interaction in a situation which presents a minimum of parameters, Diamond (6) has determined the effect on the binocular visual match between two fields of equal size (designated here as test and reference fields) imaged independently on the two foveas when a third inducing field of the same size is presented adjacent to one of them.…”