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Saeideh Ghahghaei, Suzanne McKee, Preeti Verghese; The precision of stereopsis in the lower visual field.. Journal of Vision 2016;16(12):826. doi: 10.1167/16.12.826.
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© 2017 Association for Research in Vision and Ophthalmology.
Macular degeneration (MD) results in vision loss in and around the fovea. When both eyes are affected, and there is binocular central field loss, individuals often adopt a peripheral preferred retinal locus (PRL) at the margin of the scotoma, with the scotoma above it and relatively intact visual field below this gaze position. We have shown previously that individuals with MD can benefit from stereopsis when roughly corresponding areas in the two eyes are used to view a target in depth (Verghese et al, 2014 ARVO). Depth perception can also be useful for navigation to avoid falling. For example, a curb with a drop of 15 cm subtends a disparity of 3 to 8 arcmin at a distance of 1 to 2 m, assuming an eye height of 150 cm and interpupillary distance of 6 cm. To determine whether intact peripheral retina has the disparity sensitivity to support such discrimination, we mapped stereoacuity thresholds across the lower visual field (horizontal, vertical and diagonal meridians) in three normally sighted participants. Consistent with previous studies (Fendick & Westheimer, 1983), our results show that stereoacuity declines as a function of eccentricity, roughly doubling every 3 degrees. Importantly, we find that stereoacuity in the lower visual field is 4 arcmin or better for eccentricities up to 14 degrees, which is near the limit of observed PRL distance from the old fovea in individuals with macular degeneration. This suggests that individuals with intact peripheral retina up to about 14 degrees eccentricity in the lower visual field have the potential to detect a curb drop off and avoid falling.
Meeting abstract presented at VSS 2016
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