To measure the amount of ocular deviation in strabismus patients with an eye-tracking virtual reality headset

Po-Han Yeh,Ming-Hui Sun,Chun-Hsiu Liu,Yih-Shiou Hwang,Sheng-Chu Chi

doi:10.1186/s12886-021-02016-z

Po-Han Yeh, Ming-Hui Sun + Show 3 more

Open Access

https://doi.org/10.1186/s12886-021-02016-z

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Abstract

PurposeTo investigate the accuracy of a newly developed, eye-tracking virtual reality (VR)-based ocular deviation measurement system in strabismus patients.MethodsA VR-based ocular deviation measurement system was designed to simulate the alternative prism cover test (APCT). A fixation target was made to alternate between two screens, one in front of each eye, to simulate the steps of a normal prism cover test. Patient’s eye movements were recorded by built-in eye tracking. The angle of ocular deviation was compared between the APCT and the VR-based system.ResultsThis study included 38 patients with strabismus. The angle of ocular deviation measured by the VR-based system and the APCT showed good to excellent correlation (intraclass correlation coefficient, ICC = 0.897 (range: 0.810–0.945)). The 95% limits of agreement was 11.32 PD. Subgroup analysis revealed a significant difference between esotropia and exotropia (p < 0.001). In the esotropia group, the amount of ocular deviation measured by the VR-based system was greater than that measured by the APCT (mean = 4.65 PD), while in the exotropia group, the amount of ocular deviation measured by the VR-based system was less than that of the APCT (mean = − 3.01 PD). The ICC was 0.962 (range: 0.902–0.986) in the esotropia group and 0.862 (range: 0.651–0.950) in the exotropia group. The 95% limits of agreement were 6.62 PD and 11.25 PD in the esotropia and exotropia groups, respectively.ConclusionsThis study reports the first application of a consumer-grade and commercial-grade VR-based device for assessing angle of ocular deviation in strabismus patients. This device could provide measurements with near excellent correlation with the APCT. The system also provides the first step to digitize the strabismus examination, as well as the possibility for its application in telemedicine.

Highlights

There are several methods to measure the amount of ocular deviation, including the Krimsky test, the alternative prism cover test (APCT), and the simultaneous prism cover test
Our study demonstrates the intra-class correlation coefficient (ICC) between the APCT and Virtual reality (VR) is good-to-excellent (0.897) for all deviation types, and is even better in the esotropia subgroup (0.962)
Our study reveals that the standard deviation in the exotropic subgroup is much higher than in the esotropic subgroup, and the ICC is lower in the exotropic subgroup compared to that in esotropic subgroup

Summary

Introduction

There are several methods to measure the amount of ocular deviation, including the Krimsky test, the alternative prism cover test (APCT), and the simultaneous prism cover test. The current standard to measure objective deviation is the APCT. There are some commercial VR headsets with built-in eye tracking, which mostly utilize the signal detected by the infrared camera. The infrared camera detects the position of the central pupil in relation to the corneal reflex [4]. There are few devices which measure ocular deviation by a VR-based system, and exact correlation with the APCT is unknown [5]. We attempted to simulate the prism cover test in an environment of VR, and to compare measurement correlations with the traditional APCT in strabismus patients

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