G L Goodrich, R Ludt
VA Palo Alto Health Care System, Western Blind Rehabilitation Center, Palo Alto, CA, United States
Visual impairment is a causal element in 18% of all falls resulting in hip fracture, and the fear of falling leads many visually impaired elders to curtail their travel. Current clinical assessments measure visual acuity, visual field, and contrast sensitivity to assess visual ability, and studies have shown that efficiency of mobility can be measured by percent-preferred walking speed (PPWS). Studies also use contacts with objects in the environment to assess visual ability to avoid obstacles, however whether contacts are measured in either the laboratory or real world settings they are relatively rare events and therefore have limited utility to assess visual mobility performance. We report on an assessment technique which we believe directly assesses functional vision for mobility and a modification of the technique which allows for the prediction of improvement in functional vision for mobility following perceptual training in object recognition. Three types of environmental hazards are assessed: a curb, a surface obstacle, and an overhanging obstacle. We report on 150 subjects assessed and trained using this procedure. The results show clinically and statistically significant increases in visual detection distance (i.e., from inability to detect a curb by over half the subjects to over 95% able to detect it from 1.75 meters or more) for all three types of hazards, and the prediction is highly correlated with the final assessment (i.e., r = 0.6 to r = 0.8). We will discuss the limitation of the current study and suggest areas for future research.
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