Orientation and Mobility Assessment in Retinal Prosthetic Clinical Trials

Abstract

The purpose of this study was to develop an orientation and mobility (O&M) assessment protocol to implement in subjects who have been implanted with an artificial silicon retina (ASR), and to use this experience to propose a research agenda for O&M with prosthetic vision. A controlled and naturalistic assessment was developed that included walking a prescribed obstacle course and travel to and from a hospital cafeteria. Subjects were tested before and 3 and 6 months after being implanted with the ASR. Outcome measures were walking speed and number of contacts with obstacles. The experiences from this study led to a proposed research agenda in O&M. Eight subjects with retinitis pigmentosa participated in this study. The vision status of the subjects ranged from <20/1600 to 20/80 visual acuity and visual fields of <5 to 40°. Using a repeated-measures analysis of variance, no differences were found in the primary outcome measures. Four subjects were observed to have reduced mobility after implantation. Three subjects self-reported enhancements of travel after implantation, but this enhancement was not observed. This study demonstrates that mobility might not be improved with prosthetic vision. The proposed research agenda emphasizes the importance of developing individualized assessments, identifying specific items of orientation rather than mobility for measuring the effect of prosthetic vision, and to develop and evaluate instructional programs that may be needed to obtain the full benefit of the technology.