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The Argus II Retinal Prosthesis System (Second Sight Medical Products) is providing a safe option for restoration of some visual function in patients with severe vision loss associated with retinitis pigmentosa.
Reviewed by Lyndon da Cruz, MD, and Jessy D. Dorn, PhD
London and Sylmar, CA-Recently published results from an ongoing 10-year clinical study of a retinal prosthesis system (Argus II Retinal Prosthesis System, Second Sight Medical Products) showed that the device has continued to maintain a high safety profile as of the 5-year time point in 30 patients with retinitis pigmentosa implanted with the device.
One additional serious adverse event occurred following the 3-year evaluation. Patients’ visual function also continued to be significantly better when tested using the device compared with the visual function when the device was turned off.
The authors published their interim findings online in Ophthalmology. The patients will continue to be followed for an additional 5 years.
“[It] is the first retinal prostheses approved for commercialization in the European Economic Area that can help restore some visual function in patients with retinitis pigmentosa, and the only one to receive FDA approval in the United States and Health Canada approval,” according to Lyndon da Cruz, MD, consultant ophthalmic surgeon, Department of Vitreoretinal Surgery, Moorfields Eye Hospital, London, and lead author of the Ophthalmology paper.
The prospective, single-arm trial is being conducted at 10 centers in the United States and Europe. Thirty participants were enrolled and each was implanted with an electrode array on the surface of the retina of the worse-seeing eye. The patients wore glasses on which a video camera had been mounted and carried a video processing unit in their pocket or slung over their shoulder, explained Jessy Dorn, PhD, study co-author and senior director of Clinical and Scientific Research, Second Sight Medical Products. The latter component converted the images into stimulation patterns sent wirelessly to the electrode array.
The primary study endpoint was safety; the investigators recorded the number, type, and the severity of the serious or non-serious adverse events that were associated with the surgery itself or the device. Visual function, which was assessed using three computer-based objective tests, was the second primary endpoint.
All of the visual assessments were performed with the device turned on and off, with the latter relying only on residual vision. Secondary endpoints included a number of vision-related tasks that the patients were asked to perform in the “real world” to determine the practicality of the device and assessments using questionnaires.
At the 5-year time point, 24 patients still had the prosthesis system implanted and functioning. None of the 30 patients were completely lost to follow-up at 5 years. Safety data could be obtained from 27 patients at that evaluation, as three devices were explanted between 1.2 and 4.3 years after surgery. The reasons for explanation were recurrent conjunctival erosions in two patients and hypotony and ptosis in one patient, Dr. da Cruz reported.
At the 3-year time point, 18 (60%) of the 30 patients had no serious adverse event related to surgery or the device. In the remaining 12 patients, 24 serious adverse events occurred, all of which were treatable and no patient required enucleation. By 5 years, only one additional adverse event, a rhegmatogenous retinal detachment, which occurred at 4.5 years postoperatively and was treated successfully.
By the 5-year evaluation, two implants failed because of the inability to maintain the radio-frequency link between the antenna mounted on the glasses and the antenna implanted in the eye, Dr. Dorn explained.
“Overall, the patients performed better on computerized and real-life tests to evaluate their level of functional vision when they wore the system compared to when the system was turned off,” Dr. da Cruz said.
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For example, when patients were instructed to find a white square on a black background of the computer screen, 81% of them scored significantly better using the system, he explained, noting about half of the patients did better while using the system for identifying the direction in which a bar was moving across the screen.
Based on the safety and performance results of the device, it was approved in the United States, Europe, and Canada.
“The device has gone on to be implanted in many patients; in many countries, it remains the only currently available treatment for profound vision loss resulting from [retinitis pigmentosa] and outer retinal dystrophy,” the authors concluded. “The new long-term data from the original study continue to demonstrate that this therapy remains an option for patients with [retinitis pigmentosa] and may allow for stable and reliable restoration of some basic visual function.”
Lyndon da Cruz, MD
Jessy D. Dorn, PhD