Abstract
Purpose :
Current rehabilitation for visual field loss frequently involves computer and screen-based visual search tasks. This experiment was conducted to determine if the new generation of low-cost remote video eye trackers are suitable to measure eye movements whilst patients complete visual search tasks and could therefore be considered for use in rehabilitation training.
Methods :
Twenty-six visually normal participants aged (mean ± S.D.) 21.36 ± 2.48 years performed a visual search task on a 17” VDU at 60cm without head restraint. The search was conducted under normal viewing (NV) conditions and with a simulated visual field defect (SVFD) of right sided homonymous hemianopia locked to the participant’s binocular eye position. In each condition there were 96 trials with targets which comprised 16 everyday objects presented in 6 different arrangements on a crowded background. During each trial, the eyes binocular position was recorded with a Tobii EyeX video eye tracker at 60 Hz. All trials were conducted under one condition then the other with the order randomised. Search time, maximum saccadic speed and the length of the scanpath were assessed offline.
Results :
There was a significant (p<0.05) correlation between search time and the length of the scanpath. Search times (SVFD: 1.56 ± 0.03s, NV: 1.00±0.03s) and scanpath lengths (SVFD:72.5±3.2mm NV:51.0±2.9) were significantly longer in the SVFD trials compared to the normal condition (p<0.01). This was due to an increase in the length of the scanpath in the hemianopic field while search times between the SVFD and NV condition were similar when the target was in presented the visible part of the field (p = 0.26). Maximum velocities of eye movements also varied between the two conditions (SVFD mean±SD: 33.59±0.52°/s, NV: 41.63±1.06) and were significantly lower in the SVFD condition (p<0.01). The search time, scanpath and eye movement speed did not improve with practice.
Conclusions :
Results of increased search time and scanpath with SVFD match previous research. The low-cost, remote video eye tracker was able to reliably quantify differences in visual search behaviour with a simulated visual field defect. Remote video eye trackers have the potential to improve the visual rehabilitation of patients with VF loss due to their ability to monitor eye movements, provide feedback and quantify progress during the rehabilitation process.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.