Distribution of Globe Excursions Within the Orbits Monitored by Eye Tracking Glasses in Ambulatory Subjects Engaged in Their Normal Daily Activities.

PURPOSE: It is unknown how gaze angle deviates over the course of normal daily activities, and whether its distribution is affected by vergence. To address these issues, an eye tracker was used to record eye positions in ambulatory subjects engaged in their usual pursuits.

METHODS

Twenty-seven normal subjects with a mean age of 23.6 years (range, 4-68 years) wore the eye tracking glasses, generating 328 min/person of usable data. Histograms were compiled to show the distribution of (1) horizontal gaze angles, (2) vertical gaze angles, and (3) vergence.

RESULTS

The histogram of horizontal gaze angles showed a bimodal distribution of vergence, with a distance peak at 1.6° and a near peak at 7.6°. The mean standard deviation of eye position was greater during far viewing (8.93°) than near viewing (6.65°). Horizontal eye position deviated by more than 25° from primary position less than 1% of the time. Vertical eye position shifted from a mean of -3.58° during far viewing to -8.54° during near viewing. Overall, the standard deviation of vertical eye position (11.63°) was greater than that of horizonal eye position (8.41°).

CONCLUSIONS

Deployment of a mobile eye tracker has revealed four main findings about eye position in the orbit. First, horizontal gaze angle remains within ±16.8° of primary gaze 95% of the time, reflecting an aversion to large horizontal ocular excursions. Second, mean vertical gaze position is shifted downward (-5.19°). Third, increased vergence is associated with a gaze shift downward. Fourth, increased vergence reduces the distribution of horizontal eye positions.