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Retinal implant holds potential for end-stage AMD patients
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 Mark Humayun |
KAANAPALI, Hawaii — A prosthetic device surgically implanted on the retina of patients with retinitis pigmentosa also shows promise for use in patients with end-stage age-related macular degeneration, according to a presenter here.
Approximately 90% of inner retinal neurons remain in patients with end-stage AMD, despite a near total loss of photoreceptors, according to Mark Humayun, MD, PhD, who presented an update on the Argus II (Second Sight Medical Products) retinal implant at Retina 2011.
Additionally, these patients' peripheral vision remains intact, he said.
"In [retinitis pigmentosa], if we replace the central vision, [patients] still have tunnel vision. The rest of the contextual information is gone," Dr. Humayun said. "But in AMD, they know other things about the periphery. You just have to fill in that middle. In many ways, it will actually be easier if we can just get the resolution up."
The Argus I utilized a 16-electrode grid and achieved visual acuity of approximately 20/4000, whereas the Argus II, with 60 electrodes, has achieved visual acuity of 20/1260. The number of electrodes and their spacing on the retina are predictive of visual acuity, Dr. Humayun said.
A newer, 240-electrode model is currently doing well in preclinical trials with four patients, according to Dr. Humayun. Second Sight anticipates receiving the CE mark in Europe this year, with U.S. Food and Drug Administration approval to follow. In order to be granted FDA approval, U.S. trials must increase the number of patients involved and demonstrate the benefit these devices are providing in activities of daily living, he said.
- Disclosure: Dr. Humayun is a consultant to and stockholder in Second Sight Medical Products.
The prospect of being able to improve central visual function in our patients with end-stage age-related macular degeneration using a retinal implant is very exciting. We do not expect to have any other treatments to help these patients anytime in the near future other than the telescopic lens implant and so there will be a significant unmet need for years to come.
End-stage AMD falls into two general categories, atrophic and fibrotic. Both could potentially be helped with the newer, higher resolution, 240-electrode implant under study. However, because the implant needs to lay flat on the retinal surface, the cases with large, thick disciform scars are likely to be more challenging. For such cases, there may need to be some degree of design modification in terms of how the device is fixated onto the retinal surface. Nonetheless, this problem should be relatively easy to overcome knowing the capability and expertise of Dr. Humayan and his team working on the project.
– Carl D. Regillo, MD
OSN Retina/Vitreous
Board member
Disclosure:Dr. Regillo is a consultant for Alcon, Allergan,
AMO, Genetech and GSK and has additional financial interests in NeoVista,
Novartis, Regeneron, Second Site and Vision Care.
Hawaiian Eye and Retina 2012 will be held January 15-20 at the Grand Wailea Resort & Spa in Maui. Learn more at OSNHawaiianEye.com or RetinaMeeting.com.