Effects of simulated visual impairment on orientation, shape, and emotion perception

Abstract

Visual impairment is reduced vision resulting from conditions that cannot be corrected by usual means like corrective lenses, and its prevalence is increasing as the lifespan of the population increases. We explore the effects of digitally simulated visual impairment on orientation, shape, and emotion perception in individuals with normal vision. Relative effects of blur and contrast reduction were examined by equating impairment levels via visual acuity; we determined levels of each impairment type needed to reduce visual acuity to 20/40 or 20/60 levels. These impairment levels were then applied to 1.5 and 4.5 cpd Gabor stimuli to measure effects on tilt thresholds, 3- and 4-lobed radial frequency (RF) patterns to measure effects on shape discrimination thresholds, and eyes extracted from emotional face stimuli to measure effects on emotion categorization. Both levels of contrast reduction increased tilt thresholds at both frequencies. 20/40 blur had no effect on tilt thresholds while 20/60 blur increased tilt thresholds only at 4.5 cpd. Similar results were obtained in the shape paradigm in which amplitude thresholds required to distinguish 3- and 4-lobed RF patterns were measured; contrast reduction and only 20/60 blur increased shape thresholds. Surprisingly, similar results were also obtained for an emotion categorization task. Subjects were asked to categorize the emotion expressed by eye images as happy, sad, angry, fearful, or surprised. Reduced contrast and 20/60 blur impaired performance. The only stimulus across all our experiments to be affected by 20/40 blur was the categorization of the happy expression. In conclusion, contrast reduction that is mild enough to earn a driver’s license (20/40) can affect orientation, shape, and emotion perception. For the stimuli used, blur affects the perception of spatial forms and emotion via eyes only at moderate 20/60 levels, except for the categorization of happy which is also affected at mild levels.

Acknowledgement: Support for this project was provided by three PSC-CUNY Awards (68197-00 46, 69702-00 47, 61251-00 49 to A. Li), jointly funded by The Professional Staff Congress and The City University of New York