Quotidian Profile of Vergence Angle in Ambulatory Subjects Monitored with Wearable Eye Tracking Glasses

PURPOSEWearable tracking glasses record eye movements and fixations as ambulatory subjects navigate their environment. We tested the performance of eye tracking glasses under laboratory and real world conditions, to characterize the vergence behavior of normal individuals engaged in their customary daily pursuits. METHODSTo define the accuracy and variability of the eye tracking glasses, 4 subjects fixated with the head stabilized at a series of distances corresponding to vergence demands of: 0.25, 0.50, 1, 2, 4, 8, 16, and 32{degrees}. Then, 10 subjects wore the eye tracking glasses for prolonged periods while carrying out their normal activities. Vergence profiles were compiled for each subject and compared with interpupillary distance. RESULTSIn the laboratory the eye tracking glasses were comparable in accuracy to remote video eye trackers, outputting a mean vergence value within 1{degrees} of demand at all angles except 32{degrees}. In ambulatory subjects the glasses were less accurate, due to tracking interruptions and measurement errors, only partly mitigated by application of data filters. Nonetheless, a useful record of vergence behavior was obtained in every subject. Vergence angle often had a bimodal distribution, reflecting a preponderance of activities at near (mobile phone, computer) or far (driving, walking). Vergence angle was highly correlated with interpupillary distance. CONCLUSIONSWearable eye tracking glasses provide a history of vergence angle and the corresponding scene witnessed by ambulatory subjects. They offer insight into the diversity of human ocular motor behavior and may become useful for diagnosis of disorders that affect vergence, such as convergence insufficiency, Parkinson disease, and strabismus.