Virtual reality-based measurement of ocular deviation in strabismus.

BACKGROUND AND OBJECTIVE

Strabismus is an eye movement disorder in which shows the abnormal ocular deviation. Cover tests have mainly been used in the clinical diagnosis of strabismus for treatment. However, the whole process depends on the doctor's level of experience, which could be subjected to several factors. In this study, an automated technique for measurement of ocular deviation using a virtual reality (VR) device is developed.

METHODS

A VR display system in which the screens that have the fixation target are changed alternately between on and off stages is used to simulate the normal strabismus diagnosis steps. Patients watch special-designed 3D scenes, and their eye motions are recorded by two infrared (IR) cameras. An image-processing-based pupil tracking technique is then applied to track their eye movement. After recording eye motion, two strategies for strabismus angle estimation are implemented: direct measurement and stepwise approximation. The direct measurement converts the eye movement to a strabismus angle after considering the eyeball diameter, while the stepwise approximation measures the ocular deviation through the feedback calibration process.

RESULTS

Experiments are carried out with various strabismus patients. The results are compared to those of their doctors' measurement, which shows good agreement.

CONCLUSIONS

The results clearly indicate that these techniques could identify ocular deviation with high accuracy and efficiency. The proposed system can be applied in small space and has high tolerance for the unexpected head movements compared with other camera-based system.