Towards clinical trials of a novel Bionic Eye: Building evidence of safety and efficacy

In the quest for therapeutic solutions for the visually impaired, electrical stimulation of the retina is, and has been, the focus of intense research. Some of these efforts have led to the development of the Phoenix99 Bionic Eye, a device which combines promising technological features with novel stimulation strategies. For medical devices, considerable challenges must be overcome before they’re allowed to be trialled in their target population. The requirements for a study to be performed include the demonstration of a positive risk-benefit ratio of the research. The present dissertation is an attempt to address how pre-clinical trials in animals can be used to understand and minimise risks. A positive risk-benefit ratio means that the potential benefits of the research outweigh the risks of the intervention. In the case of retinal prostheses, the risks include the surgical intervention, the immune response to the device, the safety of the electrical stimuli, and the effects of device ageing. In this work, successful demonstration of the surgical safety and biocompatibility of passive Phoenix99 devices during long-term implantation in sheep called for the evaluation of the chronic effects of the novel stimulation paradigms it can deliver. As preparation for this study, the techniques used to evaluate the safety and efficacy of the stimuli in animals were refined. A systematic approach to minimise the impact of anaesthesia on the experimental results is presented, as well as a novel in vivo retinal recording technique. To maximise the clinical relevance of all animal trials, a computer model for the prediction of thresholds was developed. Finally, in vitro device ageing was performed to deepen our understanding of the design’s potential for long-term implantation. Protocols for a long-term device safety study in sheep and for an acute human trial are also presented, thus taking concrete and sensible steps towards the first clinical use of the Phoenix99 Bionic Eye

Implantation and long-term assessment of the stability and biocompatibility of a novel 98 channel suprachoroidal visual prosthesis in sheep

Severe visual impairment can result from retinal degenerative diseases such as retinitis pigmentosa, which lead to photoreceptor cell death. These pathologies result in extensive neural and glial remodelling, with survival of excitable retinal neurons that can be electrically stimulated to elicit visual percepts and restore a form of useful vision. The Phoenix99 Bionic Eye is a fully implantable visual prosthesis, designed to stimulate the retina from the suprachoroidal space. In the current study, nine passive devices were implanted in an ovine model from two days to three months. The impact of the intervention and implant stability were assessed using indirect ophthalmoscopy, infrared imaging, and optical coherence tomography to establish the safety profile of the surgery and the device. The biocompatibility of the device was evaluated using histopathological analysis of the tissue surrounding the electrode array, with a focus on the health of the retinal cells required to convey signals to the brain. Appropriate stability of the electrode array was demonstrated, and histological analysis shows that the fibrotic and inflammatory response to the array was mild. Promising evidence of the safety and potential of the Phoenix99 Bionic Eye to restore a sense of vision to the severely visually impaired was obtained