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

Purpose: Wearable eye trackers record gaze position as ambulatory subjects navigate their environment. Tobii Pro Glasses 3 were tested to assess their accuracy and precision in the measurement of vergence angle. Methods: Four subjects wore the eye tracking glasses, with their head stabilized, while fixating at a series of distances corresponding to vergence demands of: 0.25, 0.50, 1, 2, 4, 8, 16, and 32°. After these laboratory trials were completed, 10 subjects wore the glasses for a prolonged period while carrying out their customary daily pursuits. A vergence profile was compiled for each subject and compared with interpupillary distance. Results: In the laboratory, the eye tracking glasses were comparable in accuracy to remote video eye trackers, outputting a mean vergence value within 1° of demand at all angles except 32°. In ambulatory subjects, the glasses were less accurate, due to tracking interruptions and measurement errors, partly mitigated by the application of data filters. Nonetheless, a useful record of vergence behavior was obtained in every subject. Vergence profiles often had a bimodal distribution, reflecting a preponderance of activities at near (mobile phone and computer) or far (driving and walking). As expected, vergence angle correlated with interpupillary distance. Conclusions: Wearable eye tracking glasses make it possible to compile a nearly continuous record of vergence angle over hours, which can be correlated with the corresponding visual scene viewed by ambulatory subjects. Translational Relevance: This technology provides new insight into the diversity of human ocular motor behavior and may become useful for the diagnosis of disorders that affect vergence function such as: convergence insufficiency, Parkinson disease, and strabismus.

Ambulatory Monitoring With Eye Tracking Glasses to Assess the Severity of Intermittent Exotropia.

PURPOSE: To explore the utility of eye tracking glasses in patients with intermittent exotropia as a means for quantifying the occurrence of exotropia, defined as the percentage of time that the eyes are misaligned. DESIGN: Prospective observational study. METHODS: Eye tracking glasses were used to obtain 68 recordings in 44 ambulatory patients with a history of intermittent exotropia. Vergence angle was monitored for up to 12 hours to document the occurrence of exotropia. RESULTS: Intermittent exotropia was present in 31 of 44 patients. They had a mean exotropia of 19.3 ± 5.3° and a mean occurrence of 40% (range 3-99%). There was a moderate correlation between the magnitude of exotropia and its occurrence (r = 0.59). In 13 patients the occurrence of exotropia was <1%; they were deemed to have an exophoria only. In 35 of 44 cases, families reported an occurrence of intermittent exotropia greater than that measured by the eye tracking glasses. CONCLUSIONS: Eye tracking glasses may be a useful tool for quantifying the severity of intermittent exotropia and for defining more precisely its clinical features.