A Study of Some Aspects of Peripheral Visual Acuity

A study of the decrement of peripheral visual acuity in eight primary meridians at increasing distances from the point of regard was undertaken in this research. Apparatus consisting of tangent screens at right angles and at twenty foot distances from the subject, a half‐silvered mirror, and an electronic illumination timer was constructed to insure conditions of photopia. constant fixation, and absence of cues in the presentation of the peripheral targets. Landolt rings from 0.2 to 2.0. decimal visual acuity, were used as targets. These were presented a sufficient number of times at each point so that data could be established which, after correction for guess, could be used in the constant process. By means of the Urban‐Mueller tables the limens for the point of regard and for each meridional point at increasing angular distances from it were derived. Curves for the data of each of eight subjects, ages 11 to >6. were computed. Composite data for the group were likewise studied. The data obtained in this study indicate that peripheral visual acuity tends to decrease at increasing distances from the point of regard more rapidly than indicated in previous studies. It was observed also that peripheral visual acuity follows closely the curve of the retinal V cones /mm 2 , and thai variance of meridional peripheral visual acuity thresholds decreases in relation to the distance away from the point of regard Individual differences in maintaining levels of peripheral acuity are pronounced.