Optimization and Validation of a Virtual Reality Orientation and Mobility Test for Inherited Retinal Degenerations.

Purpose: To optimize a virtual reality (VR) orientation and mobility (O&M) test of functional vision in patients with inherited retinal degenerations (IRDs). Methods: We developed an O&M test using commercially available VR hardware and custom-generated software. Normally sighted subjects (n = 20, ages = 14-67 years) and patients with IRDs (n = 29, ages = 15-63 years) participated. Individuals followed a dim red arrow path to a "course exit," while trying to identify nine obstacles adjacent to, or directly in their path. Dark-adapted subjects completed 35 randomly selected VR courses at increasing luminances, twice per luminance step, binocularly, and uni-ocularly. Performance was graded automatically by the software. Patients with IRD completed a modified Visual Function Questionnaire (VFQ). Results: Normally sighted subjects identified approximately 50% of the obstacles at the dimmest course luminance. Except for two patients with IRD with poor vision, all patients were able to complete the test, although they required brighter (by >2 log units) luminances to identify 50% of the obstacles. In a single-luminance screening test in which normal subjects detected at least eight of nine objects, most patients with IRD underperformed; their performance related to disease severity, as measured by visual acuity, kinetic visual field extent, and VFQ scores. Test-retest differences in object detection were similar to the differences between the two eyes (±2 SD = ±2 objects). Conclusions: This VR-O&M test was able to distinguish subjects with IRDs from normal subjects reliably and reproducibly. Translational Relevance: This easily implemented, flexible, and objectively scored VR-O&M test promises to become a useful tool to assess the impact that IRDs and their treatments have on functional vision.