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Toronto (Oct. 13, 2014) – In a Canadian first, Dr. Robert Devenyi and his surgical team at the Donald K. Johnson Eye Centre of the Krembil Neuroscience Centre successfully implanted a retinal prosthesis that stimulates the eye and restores functional vision in patients with forms of advanced retinitis pigmentosa (ARP).
On June 5, the first patient underwent a surgical procedure to receive the Argus Retinal Prosthesis System (Argus II) as part of an observational study to collect additional information about the safety of the device, and how it affects subjects' vision. The patient returned home the same day as the surgery, and continues to participate in regular rehabilitation appointments to refine her use of the technology.
"We are thrilled to be the first and only centre in Canada to perform this procedure and provide this technology to patients suffering from degenerative blindness," said Devenyi, Ophthalmologist-in-Chief and Director, Retinal Services, UHN. "Our centre has both the necessary surgical expertise and low vision clinic to support the recovery and rehabilitation that patients need following surgery, and we hope to eventually help many more patients with this implant."
In a healthy eye, the photoreceptors in the retina convert light into tiny electrochemical pulses that are sent through the optic nerve and into the brain, where they are decoded into images. If the photoreceptors no longer function correctly due to conditions such as ARP, the first step in this process is disrupted and the visual system cannot transform light into images.
The Argus II bypasses the damaged photoreceptors through several electrodes implanted on the surface of the retina. Patients wear glasses containing a miniature camera that convert captured video images into a series of small electrical pulses that are transmitted wirelessly to the electrodes. The pulses stimulate the retina's remaining cells which transmit the visual information along the optic nerve to the brain. Although the vision provided is not the same as regular sight, it allows the patient to perceive patterns of light.
Following surgery, patients worked with rehabilitation specialists to learn how to perform everyday tasks using the Argus II system and interpret the visual information captured by the device. Researchers also conducted regular tests to study which electrodes create a visual reaction in patients when stimulated. Future follow-up visits will occur in the patient's home under direction of low vison therapists who will help them refine the use of their device.
"The potential change in vision this device offers patients is remarkable," said Dr. Samuel Markowitz, a low-vision rehabilitation specialist at Toronto Western Hospital working with the study participants.
"Having spent my career helping patients adapt to losing their sight, it is so satisfying to now work with patients who have been essentially blind their whole lives relearn how to process visual information."
Developed by the California-based company Second Sight, the Argus II is the first and only retinal prosthesis approved in the US and Canada.
Funding for the implants was provided by the Toronto General & Western Hospital Foundation which raises funds for research, education and the enhancement of patient care, as well as the Foundation Fighting Blindness that advances retinal disease research, education and public awareness to fight blindness.
With two implant procedures successfully completed, the surgical team aims to do eight more as part of the study.
The Krembil Neuroscience Centre (KNC), located at Toronto Western Hospital, is home to one of the largest combined clinical and research neurological facilities in North America. Since opening in 2001, KNC has been recognized as a world leader through its research achievements, education and exemplary patient care. The centre focuses on the advancement, detection and treatment of neurological diseases and specializes in movement disorders, dementias, stroke, spinal cord injury, blinding eye diseases, epilepsy and cancer-related conditions. For more information please visit www.krembil.com.
University Health Network consists of Toronto General and Toronto Western Hospitals, the Princess Margaret Cancer Centre, and Toronto Rehabilitation Institute. The scope of research and complexity of cases at University Health Network has made it a national and international source for discovery, education and patient care. It has the largest hospital-based research program in Canada, with major research in cardiology, transplantation, neurosciences, oncology, surgical innovation, infectious diseases, genomic medicine and rehabilitation medicine. University Health Network is a research hospital affiliated with the University of Toronto.
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