Safety concerns raised over people with peripheral field loss

Poor traffic gap judgement in patients with peripheral field loss (PFL) raises important safety concerns for their safety when crossing the road, according to a study published online by Optometry & Vision Science.

Allen Cheong and colleagues from The Minnesota Laboratory for Low-Vision Research, University of Minnesota, USA recruited eight subjects with significant PFL and five age-matched control subjects. Each subject was asked to judge when they perceived it to be safe to cross a two-way, four-lane street while they stood on the curb. Eye movements were recorded by an eye tracker and movies of the eye-on-scene were made offline. Fixation patterns were classified into either relevant or irrelevant. Patients' street-crossing behaviour, habitual approach to street crossing and perceived difficulties were also assessed.

Compared with normal vision subjects, the PFL subjects identified 12% fewer crossable gaps while making 23% more errors by identifying a gap as crossable when it was, in fact, too short (p<0.05). These differences may be explained by the significantly smaller fixation area (p=0.006) and fewer fixations distributed to the relevant tasks (p=0.001). The patients' habitual approach to street crossing and perceived difficulties in street crossing were significantly correlated with traffic gap judgment performance.

The poor traffic gap judgment of patients with peripheral field loss raises concerns about their safety in crossing streets.