Abstract
In low vision navigation, an essential ability is the accurate judgment of object locations in the environment (Ludt & Goodrich, 2002). We investigated absolute distance perception in normal vision and simulated low vision conditions to ascertain the perceptual capabilities of individuals with profound low vision. Participants were normally sighted and tested monocularly in two conditions. In the first block of trials, participants wore goggles with stick-on blur foils, resulting in a tested acuity between 20/900 and 20/2000. In the second block of trials, participants wore goggles with clear flat lenses. Participants remained naïve to the test room until after the low-acuity condition was performed. The test room was 19′ x 22′ and brightly lit. Targets were two sizes of bright orange traffic cones, located on the ground-plane at egocentric distances of 2, 2.5, 3, and 3.5 meters. In some trials, no target was present. On each trial, subjects were asked if they could see the target. If they responded affirmatively, they walked blindfolded to the apparent target location while an experimenter moved the cone out of the way. Even though in the low vision condition the orange cones appeared as barely detectable orange blobs, group-averaged data exhibited near accuracy in walked distances. Walked distances in the normal acuity condition were also accurate, consistent with many other studies, with the between-subject variability somewhat less than for the reduced acuity condition. The room in which the experiment was conducted had a molding around the floor that was visible even while wearing the acuity-reducing goggles. Future work will examine if this provided a visual context allowing use of perspective information to estimate distance, even with severely degraded vision. The effects of varying the target distances, target types, and lighting conditions will also be considered.
This work was supported by NIH grant 1 R01 EY017835-01.