Eye Movement Characteristics While Repeatedly Walking A Simple Route: Persons With Central Versus Peripheral Visual Field Loss

Abstract

Abstract: : Purpose: Persons with peripheral visual field loss (PFL) more frequently report mobility difficulty compared to persons with central visual field loss (CFL). Both groups report fewer problems as they become familiar with the environment. One possible explanation is that with experience people develop an internal representation that can be used to reduce uncertainty about the environment and guide scanning behavior. In this study we investigated whether route experience affects eye movement characteristics in persons with visual field loss and also whether it differentially affects them for persons with CFL and PFL.Methods: Subjects included 16 persons with visual field loss (6 with peripheral field loss as a result of glaucoma or retinitis pigmentosa and 10 with central field loss as a result of age–related macular degeneration and Stargardt’s disease). Subjects repeatedly walked down a hallway and turned at the 5^th door on the left. Eye movements were recorded as the subjects performed the task and were analysed offline. Number of fixations, saccadic amplitude, fixation duration, and eye–in–head fixation area for the first 3 passes were analysed and compared across time and subject group.Results: Results of a mixed ANOVA of saccade size showed a significant interaction between time and group (p=0.03). Saccades increased with time more so for subjects with PFL than those with CFL. Both groups had larger fixation areas (eye–in–head) with time, and CFL subjects had a (non–significant) trend toward larger areas than the PFL subjects. Walking speed decreased as subjects became more familiar with the environment (p<0.01). However, the number of fixations and fixation duration did not differ across time or group. Conclusions: With route experience, the spatial parameters (saccadic amplitude and fixation area) of eye movements increase for both the CFL and PFL groups. This, taken together with a lack of a decrease in fixation duration and number of fixations, suggests that experience aids walkers most in knowing where to fixate.

Keywords: eye movements • low vision • vision and action