Bionics: Seeing into the Future

In 2015, a case study was performed by the Argus II study group on the impact the implant would have on restoring visual function to subjects who had complete blindness from RP. The results from this study were quite promising; it showed that of the 30 patients who received the Argus II system, all significantly performed better on a white square test than they did without the prosthesis. (None of the subjects scored any points with the device absent.) The Argus also showed reliability for 29 subjects, all of whom still had functioning devices after three years (13).

In 2020, a clinical trial of this device for dry AMD was completed. The study, which consisted of five patients, assessed the safety and feasibility of the device. According to Mills et al. (14), no patients reported confusion when operating the Argus alongside their healthy peripheral vision. Adverse events occurred in two patients who experienced proliferative vitreoretinopathy — or tractional retinal detachment.

However, due to recent events surrounding the COVID-19 pandemic, the company declared that they would be performing “an orderly wind-down of the company’s operations”. SecondSight is now focusing on a new device: The Orion. This device is designed to stimulate the visual cortex of the brain — a return to the original conception of visual prosthetics. The Orion is planned to expand the pool of patients who are eligible for visual prosthetics. It will essentially bypass the requirement for healthy ganglion cells and a functioning optic nerve, which retinal prosthetics require. The only forms of blindness not encompassed by this technique are congenital forms of blindness or people who are ‘cortically blind’ from suffering damage to the visual cortex area V1. The Orion is modelled after the Argus II with its 60 cortical-stimulating electrodes receiving input from a camera on the user’s glasses. Under the Breakthrough Device Pathway, the FDA approved Orion for an early feasibility study. Six human subjects have been fitted with the device — one woman and five men between the ages of 29 and 57. Of these six, one had endophthalmitis, two had glaucoma, and three suffered trauma. After one year of wearing the device, four of the patients could accurately discern the location of a palm-sized white square on a computer screen, and five could locate its movement in space. The Orion has shown a good safety profile after 12 months of use, and follow-ups on its progress will occur for five years (15).
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Visual prostheses have a promising and bright future of development ahead of them. While it is still in its infancy, the results of ongoing clinical trials show promise for sight restoration. With multiple models and modes of intervention available, artificial vision is slowly becoming a reality for the visually impaired, but further developments in the field are still required. It would be promising to see advancements from mere two-dimensional grey-scale images to the rich, three-dimensional, and full-colour experience that we take for granted as normal vision. For now, two essential factors need to be improved for the full realisation of artificial vision: cost and electrode density. The Argus costs 150,000 USD — an expense that excludes surgery and training. This figure may be unfeasible for the thousands of Australians who would benefit from such a device. If the current trend of Moore’s Law continues, electrode density will increase whilst the cost of the device will decrease — a trend analogous to the increase in power and improved price of computers in the last century. This pixel density will hopefully improve to the point of achieving near-normal visual acuity. The 60 pixels, while helpful in regaining some functionality, cannot compare to the some 96 million photoreceptor cells in the retina — 5 million of which are located in the cone-dense macula. Nevertheless, artificial vision is an exciting and innovative technology currently under development. While much research is still needed, further advancements in bionics will one day make visual prosthetics a ubiquitous and affordable technology to those in need.