Automated assessment of ocular deviations using a consumer-grade eye tracker and 3D display

Abstract

Purpose: The clinical gold-standard for detecting strabismus and measuring ocular alignment are the cover/uncover test and the prism alternate cover test (PACT) respectively. Administration of these tests require skilled clinicians and considerable time, and results are variable between examiners. We investigated whether a digital alternating cover test (ACT) performed using a consumer-grade eye tracker and 3D display can provide an automated, efficient and objective assessment of eye alignment. Methods: We tested 23 adult participants (age 20-51 years, including 4 with strabismus) on both a 9-point digital ACT and a standard clinical PACT. Both tests were conducted at a 55cm viewing distance. For the digital ACT, participants wore stereo glasses and fixated/followed a target on a computer monitor, while both eyes were tracked. The target was presented monocularly and binocularly at a series of 9 locations spanning ±15° horizontally and ±12° vertically from primary gaze. Re-fixation eye movements made in response to stimulus change were used to detect strabismus and to quantify deviation angle. At least 3 measurements were taken for left and right eye fixing at each target location (total test time: 3-4 min) and the average of these values quantified deviation angle for each combination of target location and fixing eye. The digital ACT was performed twice for each participant to examine internal reliability. Results: At primary gaze, mean horizontal angle for left eye fixing was 0.24 ± SD 9.84A for the digital ACT and-2.70 ± SD 9.60A for the clinical PACT (Spearman's r = 0.86, p<0.0001), and for right eye fixing was-0.05 ± SD 9.09A for the digital ACT and-2.74 ± SD 9.32A for the clinical PACT (Spearman's r = 0.87, p<0.0001). The digital ACT measures for left and right eye fixing respectively were on average 2.9A (95% limit of agreement [LOA]: ±4.6) and 3.0A (95% LOA: ±6.1) more eso than the clinical PACT, which may be due to stimuli differences. Measurements were consistent between the two repeats of the digital ACT, with mean differences of-0.4A (95% LOA: ± 4.6) and-0.2A (95% LOA: ± 5.5) for left and right eye fixing. Conclusions: Low-cost eye trackers and 3D displays can be used to quickly assess ocular deviations at multiple gaze directions. Results strongly correlated with standard clinical PACT. This type of test may be useful in clinical settings, such as for repeated measurements or for children.L6299350422019-11-28 <br />