Preliminary Results of the Bionic Vision Australia Suprachoroidal Visual Prosthesis Pilot Trial

Abstract

Purpose: Visual prostheses have been shown to be efficacious in the restoration of basic visual percepts to patients with profound vision loss from retinitis pigmentosa (RP). Previous implants have been located in either the epiretinal, subretinal or intra-scleral spaces of the eye. Bionic Vision Australia has conducted a pilot clinical trial of a novel suprachoroidal implant. The purpose of this study was to evaluate the stability, safety and basic efficacy of the device.

Methods: Three subjects with end-stage retinitis pigmentosa (bare light perception) were implanted with a prototype silicone and platinum suprachoroidal array containing 20 stimulating electrodes, which could be directly stimulated via a percutaneous connector. Intraocular array position was monitored over an 18-month period with weekly fundus photography and optical coherence tomography (OCT) scans. Lead wire and percutaneous connector stability were monitored using monthly X-ray and biannual computerized tomography (CT) imaging. Device efficacy was assessed using psychophysical methods, and assessment of performance in basic visual function tests such as the Basic Assessment of Light and Motion (BaLM), Berkeley Rudimentary Vision Test (BRVT), tumbling E and Landolt C tests.

Results: From image analysis, both the intraocular array and extraocular connections remained in a stable position with respect to anatomical landmarks in the retinal plane. There was no damage to the devices, and the only device-related serious adverse events related to superficial skin infection around the percutaneous connector, which settled with topical or systemic antibiotics and no intraocular sequelae. All electrodes remained connected during the 18-month period. All three subjects perceived phosphene percepts, although there were significant differences in optimal stimulation parameters between them. All patients performed better with the device on than off for the laboratory based visual function tests, including achieving scores of between 72% and 100% on the light localisation subtest of the BaLM when the device was on.

Conclusions: The suprachoroidal implant location is safe and provides excellent device stability. Visual function test performance was improved with device on vs. device off. As device efficacy and longevity is dependent on a stable electrode-tissue interface, suprachoroidal implantation appears a promising option for visual prostheses.

Keywords: 696 retinal degenerations: hereditary • 467 clinical laboratory testing • 550 imaging/image analysis: clinical