title: Visual acuity with reversed-contrast charts: II. Clinical investigation.
abstract: Snellen visual acuity was measured in 106 patients ranging in age from 20 to 88 years in routine examinations in the general refraction clinic with two kinds of charts: the standard chart using black letters on a white background and a reversed-contrast display featuring white letters on a black background. The overall ratio of the white-on-black to the black-on-white Snellen fractions was 1.043. A scattergram relating this ratio to patient age revealed that the older the patient, the more the visual acuity was improved by switching to the reversed-contrast chart, with a regression line slope of 0.5 +/- 0.10. Impairment of the eye's optics, in particular by intraocular scatter causing a widening and flattening of the eye's point-spread function, explains these findings and suggests prognostic and therapeutic value of reversing the contrast polarity of displays.
authors: Division of Neurobiology, University of California, Berkeley, California 94720, USA. gwest@socrates.berkeley.edu
authors: Gerald
authors: G
authors: Westheimer
authors: Patricia
authors: P
authors: Chu
authors: Wendy
authors: W
authors: Huang
authors: Thuy
authors: T
authors: Tran
authors: Robert
authors: R
authors: Dister
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D015350:Contrast Sensitivity / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D012160:Retina / Q000502:physiology*; D014787:Vision Tests / Q000295:instrumentation*; D014792:Visual Acuity / Q000502:physiology*