THE PERIPHERAL VISUAL ACUITY OF 100 SUBJECTS UNDER SCOTOPIC CONDITIONS

Abstract

The simple form acuity of 100 subjects was measured at 14 points on the retinal periphery under scotopic (night vision) conditions and compared to similar measurements by the same technique in 100 subjects under photopic (day vision) conditions. Scotopic form acuity is weaker than photopic form acuity approx. as 7 is to 5 (low score best). Acuity isopters for night vision are nearly circular, being measureably flattened only on top, contrasting with the irregular oval isopters for day vision. The dispersion of scores in night visual acuity is less than for day visual acuity. The scotopic testing was somewhat less reliable (r = 0.84) than the same technique in photopic testing (r = 0.91). Impairment but not absence of the scotopic mechanism was observed in one case in about 150 subjects.