Abstract
Purpose :
Dissociated tests of incomitant strabismus, such as the Lancaster red-green test, Hess screen and Lees screen, provide valuable tools for diagnosis and monitoring of ocular misalignment in patients with normal retinal correspondence. However, they all lie vulnerable to operator error and rely on head fixation. Virtual reality headsets obviate the need for head fixation, whilst providing other clear theoretical advantages, including complete control over the illumination, background and nature of targets presented for the patient to interact with. We compared the performance of a virtual reality-based test of ocular misalignment to that of the traditional Lees screen, to establish the feasibility of virtual reality technology use in the diagnosis and monitoring of ocular misalignment in the future.
Methods :
Each patient recruited to this prospective study underwent a traditional Lees screen test, and a virtual reality headset-based test of ocular motility. The virtual reality headset-based program was written in PsychoPy, and consisted of an initial test to measure horizontal and vertical deviation, followed by a test for torsion. Deviations from each test were compared using Bland-Altman analysis.
Results :
The pattern of deviation obtained using the virtual reality-based test showed agreement with that obtained from the Lees screen for a variety of paretic and restrictive conditions, including fourth nerve palsy (Fig. 1), restrictive thyroid eye disease (Fig. 2).
Conclusions :
This study reports the first use of a virtual reality headset in assessing ocular misalignment, and demonstrates that it is a feasible dissociative test of incomitant strabismus. It also highlights challenges of virtual reality technology, including the deprivation of absolute depth cues leading to accommodative flux, which may limit quantification of ocular deviation.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.