Evaluation of a Novel Virtual Reality Simulated Alternate Cover Test to Assess Strabismus: A Prospective, Masked Study

Abstract

A sensorimotor examination is the gold standard for strabismus diagnosis and quantification but requires a highly skilled examiner and may be limited by a child's cooperation. Virtual reality (VR) employs eye-tracking technology to monitor eye position and may be able to measure strabismus. The aim of this study was to assess a prototype VR-simulated alternate cover test to detect and measure strabismus. Prospective, masked diagnostic test study. Patients aged 5-18 years with visual acuity of 20/80 or better were prospectively enrolled to undergo strabismus measurements using a VR simulated alternate cover test (Olleyes, Inc., Summit, NJ) followed by an alternate cover test performed by a masked pediatric ophthalmologist or orthoptist. The main outcome measure was correlation between gold standard and VR-obtained strabismus measurements (in prism diopters [PD]) in primary gaze at near using Pearson correlation coefficients and Bland-Altman analysis with limits of agreement (LOA). A secondary measure was the diagnostic accuracy for the VR headset to detect strabismus. A total of 85 participants were enrolled, mean ± standard deviation age was 10.8 ± 3.8 years, 45.9% (39/85) male. 40.0% (34/85) had strabismus: 17.7% (15/85) esotropia, 22.4% (19/85) exotropia, and 5.9% (5/85) vertical strabismus. 52.9% (18/34) of strabismus was intermittent. The overall correlation between VR and gold standard strabismus measurements was moderate but significant (r = 0.42, 95% CI 0.22, 0.58, P < .001), and correlation was strong for esotropia and constant deviations (r = 0.74, 95% CI 0.38, 0.91, P = .001 and r = 0.74, 95% CI 0.39, 0.91, P < .001, respectively). In participants with horizontal strabismus, Bland-Altman analysis showed a mean difference between standard and VR measurements of 3.55 ± 8.33 PD for esotropia (upper and lower LOA 19.89, -12.78 PD) and 17.15 ± 11.20 PD for exotropia (LOA 39.09 and -4.79 PD). Sensitivity for detecting strabismus was low: 27.6% (95% CI 12.7, 47.2), but specificity was high: 87.5% (95% CI 75.9, 94.8). A prototype VR simulated alternate cover test showed a moderate but significant correlation with the gold standard sensorimotor examination and correlation was strong in those with esotropia and constant deviations. While the level of agreement demonstrated by this novel VR technology is promising, further improvements are needed before clinical deployment. However, this study demonstrates that VR has the potential to expand our ability to detect, measure, and monitor strabismus.