ABSTRACT
BACKGROUND: The central visual field is particularly affected in age-related macular degeneration (AMD), and this can impinge on a variety of functional tasks, including navigation, which can affect activities of daily living. It has been difficult to assess navigational function under standardised conditions. The aim of this study is to examine gaze function and pupil diameter during navigation in patients with AMD. METHODS: This study was designed as an observational case-control investigation. 34 patients with AMD and 23 controls were recruited. We simulated a walking journey using video projection and monitored patients using automated eye tracking. Visual acuity, fixation count, fixation duration and pupil diameter were recorded while subjective measurements included recorded voice comments. RESULTS: The pupil diameters were significantly greater in the AMD group compared with the control group in both easy and difficult segments of navigation (p=0.002). Fixation counts were significantly higher in the AMD group during difficult segments of navigation (p=0.001). The differences in both pupil diameter and fixation count correlated with subject visual acuity. CONCLUSIONS: Fixation count is a marker of difficult navigational environments in patients with AMD. The combination of video projection and eye tracking to assess visual navigation function is a useful clinical tool and an adjunct to current investigation tools in AMD intervention studies providing objective clinical measures under standardised settings.
