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Study of tunnel vision suggests requirements for head-mounted visual aids
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People with peripheral visual field loss demonstrate reduced horizontal eye scanning when walking, compared to normally sighted people, a study found. The results should help define the requirements for head-mounted mobility visual aids for patients with disorders such as retinitis pigmentosa, the study authors said.
Fernando Vargas-Martín, PhD, of the University of Murcia, Spain, and Eli Peli, OD, of Schepens Eye Research Institute in Boston, examined the eye movements of people with severe peripheral field loss (PFL) walking in real environments. Investigators recorded eye positions relative to the head in five patients with less than 15° of visual field due to retinitis pigmentosa and in three normally sighted control subjects. Each participant walked in varied environments for more than 30 minutes, according to the study authors.
The researchers found that patients with PFL had 9.4° of horizontal eye-position dispersion, significantly narrower than the 14.2° for normally sighted subjects (P < .0001). Vertical dispersions for PFL patients averaged 8.2° when walking indoors. This was significantly narrower than the range when they were walking outdoors, which averaged 10.3° (P = 0.048).
"The results suggest that a field of view as wide as 40° may be needed for closed head-mounted mobility aids, whereas a much narrower display, perhaps as narrow as 20°, may be sufficient with an open design," the authors said.
The study is published in the December issue of Investigative Ophthalmology & Visual Science.