Abstract
Purpose :
To determine if a visually impaired person’s perception of their street-crossing ability correlates with the safety of their street-crossing decisions.
Methods :
Crossing decisions along a non-signalized street with two lanes of one-way traffic were collected from 129 visually impaired subjects classified as self-reporting either “having” or “not having” difficulties crossing the street as well as either having only visual acuity loss (VA Loss) or VA and visual field (VF) Loss (VA + VF Loss). After observing traffic for two seconds using their habitual vision and hearing, subjects were required to make a decision about whether or not they thought it was safe to cross for different vehicular gap times. The percentage of unsafe decisions (%unsafe), computed as the percentage of times subjects indicated that they would cross a measured vehicular gap time that was shorter in duration than their actual crossing time, was computed for every subject. The percentage of missed opportunities (%missed) was also calculated for each subject by computing the percentage of times subjects indicated that they would not cross a measured vehicular gap time that was longer in duration than their actual crossing time. Generalized linear mixed models with repeated measures for subject were used to determine if the %unsafe and %missed decisions changed as a function of subject group (with and without self-reported difficulties) and type of vision loss (VA Loss and VA + VF Loss).
Results :
Subjects with and without self-reported difficulties made on average 2.1% and 2.7% unsafe decisions and 16.9% and 21.2% missed decisions. No significant difference was found in the %unsafe and %missed decisions between subjects with and without self-reported difficulties in crossing the street (p=0.61 for %unsafe and p=0.43 for %missed). Those subjects however with both VA + VF Loss made significantly more unsafe decisions (6%) compared to those subjects with VA Loss only (0.9%, p<0.0001). No significant difference was found in the %missed decisions between the VA Loss (22.3%) and VA + VF Loss (16%) groups (p=0.25).
Conclusions :
Our data suggests that reporting having difficulties crossing the street does not affect a visually impaired pedestrian’s ability to make appropriate judgements about when it is safe to cross, but having both acuity and visual field loss does.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.