Search

Visual impairment (VI) can result from many different ocular diseases and is defined as the poor functioning of the visual system. To describe the extent of VI, clinical measures of visual function are used, which include visual acuity (VA), visual field (VF) and contrast sensitivity (CS). When there is a reduction in any of these visual functions, safe and efficient mobility is one such activity that may be compromised. While there is currently no cure for VI-causing retinal diseases such as retinitis pigmentosa (RP), age-related macular degeneration (AMD) and glaucoma, gene therapy is gaining traction as a possible treatment. Preliminary results have shown that patients have performed significantly better on mobility tasks, such as the navigation of an obstacle course, post-treatment. Interestingly, visual function measures have not always shown such significant improvement. It is therefore important to develop a standardized obstacle course that can assess therapy efficacy, as the drawbacks of current physical orientation and mobility obstacle courses include high cost of set-up, potential dangers to participants and the fact that performance may reflect non-visual abilities such as physical fitness. To address these concerns, we have investigated the use of a virtual obstacle course in people with visual impairment. Here we report the initial behaviors and strategies of people with visual impairment as they navigate through four obstacle tasks using a virtual reality headset.

Background: Vergence eye movements are the disconjugate movements of the two eyes, needed to accurately ‘point’ the eyes at an object of interest. Convergence insufficiency is the reduced ability to elicit and maintain the eyes in the accurate convergence position, and it affects about 5% of the population, often leading to visual symptoms such as diplopia (double vision), eye strain and headaches, especially during near tasks. The ability to converge and diverge accurately can be trained with vision training, but vision training activities are not standardized and they are often not complied with. Methods: We developed a novel virtual reality (VR) snake game and compared it with conventional anaglyph treatments in a randomized controlled trial on typical adults. Compliance was assessed by the time spent doing the prescribed vision training over a period of three weeks. Results: There was a statistically significant improvement of convergence ability in both the VR snake and anaglyph treatment groups, and no difference in compliance between the two groups. Conclusion: Virtual reality headsets may be used to train vergences in adults. Further work is required to determine its utility in people with convergence insufficiency who require training for longer than 3 weeks.

Retinitis pigmentosa (RP) causes visual field (VF) constriction due to progressive loss of photoreceptors, typically from the retinal periphery to the fovea. Retinal prostheses offer vision restoration via electrode implantation and stimulation near the fovea, thereby eliciting articifial percepts, so-called phosphenes in the center VF. Although foveal photoreceptors can persist for prolonged periods of time, bionic therapy is usually restricted to stages of RP with complete vision loss. However, persons with RP experience mobility impairment from peripherally restricted VFs much earlier. Consequently, the amount of visual scanning necessary for navigation is increased, and maintaining a steady pace is challenging. Receiving a retinal implant at this early stage might be feasible. We investigated the potential of a peripheral visual prosthesis coexisting with central residual vision to facilitate scene perception and mobility. Simulating prosthetic and residual vision in a virtual mobility environment, we found that assistive phosphene layouts were associated with reductions in visual scanning-related head movements of up to 42.1%, body rotations of up to 30%, and up to 45% lower frequency of stopping when circumventing low-lying obstacles, pedestrians and following a path. Further research on early implantation of retinal prostheses for the peripheral VF is therefore advised.