Visual impairment is reduced vision due to aging, disease, or injury that cannot be corrected by corrective lenses or surgery. We explore the effects of digitally simulated visual impairment on orientation and shape perception in individuals with normal or corrected-to-normal vision. Relative effects of blur and contrast reduction on perception were examined by equating impairment levels via visual acuity. Specifically, we determined for each subject, levels of blur and contrast reduction needed to reduce visual acuity to 20/40 (minimum acuity required to obtain a driver's license) or 20/60 levels. These impairment levels were then applied to 1.5 cpd and 4.5 cpd horizontally and vertically oriented Gabor stimuli to measure their effects on tilt thresholds. 20/40 levels of blur had no effect on tilt thresholds, however equivalent levels of contrast reduction significantly increased tilt thresholds at both frequencies. Increasing blur to 20/60 levels significantly increased tilt thresholds at 4.5 cpd (but not 1.5 cpd), owing to a higher pass blur filter. Thus even mild levels of contrast reduction, such as that commonly experienced in cataracts, can affect orientation perception. These results are predictable given the frequency content of our stimuli. However it remains to be seen whether similarly predictable effects will be obtained using more complex stimuli processed by higher order mechanisms in the visual system. Effects of blur and reduced contrast on shape perception using radial frequency patterns will be reported. Understanding effects of different forms of impairment may contribute to digital technologies to enhance vision on an individual basis.
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