Fixation behavior while walking: persons with central visual field loss.

The aim of this study was to determine the effect of central visual field loss (CFL) on fixation patterns of a person walking towards a target. Subjects were four visually normal persons and 10 persons with CFL. Eye position on scene was recorded and classified into 20 scene categories. The distributions of fixations among scene categories were compared across the two subject groups. For all but two CFL subjects, who fixated primarily at the floor, the distributions of fixations for the CFL subjects ranged from being moderately to strongly correlated with that of the visually normal mean. An analysis of the similarity in the sequence of fixations (or gaze pattern) of the CFL subjects to the visually normal subjects showed a range of 7-66%. Excluding the one CFL subject who had a functioning fovea, sequence similarity was strongly correlated with the logarithm of the minimum angle of resolution (logMAR). The better a person's logMAR, the more closely his or her gaze pattern matched that of the visually normal subjects. Finally, the CFL data were tested against two current models of oculomotor strategy, visual salience and guided search. Similar to what was found with visually normal subjects, CFL subjects appear to use the expected features and general location of the target to guide their fixations, the guided-search strategy.