OBJECTIVE: To evaluate feasibility of restoration of central vision in patients with age-related macular degeneration using a wireless photovoltaic subretinal implant. In particular, to assess safety of sub- retinal implantation and quality of prosthetic vision in patients with geographic atrophy.
MATERIAL-METHODS: A prospective study in 5 patients with visual acuity ≤20/400 due to geographic atrophy of at least 3 optic discs diameters and no foveal perception. Wireless photovoltaic chip
(PRIMA, Pixium Vision) is 2x2mm in size,30μm in thickness, containing 378 pixels of 100μm in width. Each pixel converts pulsed near-infrared light (880nm) projected from video-goggles into electric current to stimulate nearby
neurons in the inner retina nuclear layer. Several surgical techniques used, varying in anesthesia (local vs. general) and retinal reattachment (gas vs. oil)
RESULTS: In all patients, surgery lasted approximately 2 hours, chip was successfully implanted under the macula and remains stable, with a follow-up extending now to 11 months in first patient. In 3
patients chip was placed into a desired position-centrally and close to the inner retina. In 2 patients the implant ended up in suboptimal positions–one in the choroid and another off-center. All 5 patients perceive white-yellow patterns with adjustable brightness, in retinotopically correct locations within previous scotomata. No decrease in natural visual acuity was observed in any patient. All 4 patients with subretinal chip placement correctly identify bar orientation, with 93.5+/-3.8% accuracy. Out of them, all 3 patients with central placement of the implant demonstrated visual acuity with Landolt C test in the range of 20/460-20/550,which is just 15-35% below the theoretical resolution limit for this pixel size (20/400).Patients are now being tested in letter recognition, reading, and other visual tasks.
CONCLUSIONS: Wireless chip PRIMA can be safely implanted under the atrophic macula in patients with geographic atrophy and restore central visual perception with acuity close to the theoretical limit of the implant. Implantation did not reduce the natural residual visual acuity of the patients. Implants with smaller pixels are being developed.