Australian Researchers Complete Two-Year Trial of Bionic Eye

Bionic Vision Australia (BVA), a collaboration between of researchers working on a bionic eye, has announced that its prototype implant has completed a two-year trial in patients with advanced retinitis pigmentosa. Three patients with profound vision loss received 24-channel suprachoroidal electrode implants that caused no noticeable serious side effects.

Moreover, though this was not formally part of the 2012 study, the patients were able to see more light and able to distinguish shapes that were invisible to them prior to implantation. The newly gained vision allowed them to improve how they navigated around objects and how well they were able to spot items on a tabletop.

The next step is to try out the latest 44-channel device in a clinical trial slated for next year and then move on to a 98-channel system that currently is in development.

“This study is critically important to the continuation of our research efforts and the results exceeded all our expectations,” professor Mark Hargreaves, chair of the BVA board, said in a statement. “We have demonstrated clearly that our suprachoroidal implants are safe to insert surgically and cause no adverse events once in place. Significantly, we have also been able to observe that our device prototype was able to evoke meaningful visual perception in patients with profound visual loss.”

BVA’s devices operate by employing electrical stimulation to bypass defunct photoreceptor cells and to stimulate remaining viable retinal cells, inducing light and visual perception in blind individuals. The BVA systems convert video images captured by a miniature camera housed in a patient’s glasses into a series of small electrical pulses that are transmitted wirelessly to an array of electrodes that are implanted on the surface of the retina. These pulses are intended to stimulate the retina’s remaining cells, resulting in a corresponding perception of patterns of light in the brain. Following the implant surgery patients learn to interpret these visual patterns thereby regaining some functional vision, allowing them to detect shapes of people and objects in their surroundings.

The ultimate aim of a retinal prostheses/bionic eye is to improve vision while also retaining any existing residual function. Preserving the retina during surgery by minimizing damage is imperative, experts claim. However, other attempts to implant epiretinal and subretinal devices in patients have resulted in a significant number of adverse events. Some of the adverse events associated with other bionic eye models include hypotony (low intraocular pressure often associated with decreased vision) and a 10-times higher rate of infection (endophthalmitis) than is normal in intraocular surgery in epiretinal prosthesis implantation. To reduce the risks of adverse events, the BVA team developed a suprachoroidal surgical procedure where the device is implanted inside the layer of loose connective tissue situated between the choroid and sclerotic coats of the eyeball. This not only reduces the risk of adverse events as a result of surgery but it also provides the device a more stable location than the other locations, BVA researchers said.

There were no adverse events reported during BVA’s proof-of-concept clinical trial involving three patients. This surgical technique will be used for all BVA wide-view devices. The suprachoroidal positioning offers other long-term advantages over epi- and subretinal implantation, BVA officials noted. Direct contact between neurons and stimulating electrodes can and often does lead to the death of neural tissue. It is believed that one of the key reasons that cochlear implants function so well for so long is that there is a ‘buffer’ in the form of fluid and bone separating the electrodes from the neural tissue they target for stimulation. In the case of the BVA wide-view devices, the suprachoroidal space where the electrodes are placed provides a very similar situation to that of the cochlear implant experience. This may be key to the longevity of a bionic eye that will be required to meet the needs of patients for several decades, the team claims.

Bionic Vision Australia is a national consortium of researchers comprised of experts from the Bionics Institute, the Centre for Eye Research Australia, National ICT Australia, the University of Melbourne and the University of New South Wales with additional project partners including the National Vision Research Institute, the University of Western Sydney and the Royal Victorian Eye and Ear Hospital. BVA is an initiative of the Australian Research Council.