Photovoltaic Restoration of Central Vision in Atrophic Age-Related Macular Degeneration

Abstract

Purpose: Loss of photoreceptors in atrophic age-related macular degeneration results in severe visual impairment, although some peripheral vision is retained. To restore central vision without compromising the residual peripheral field, we developed a wireless photovoltaic retinal implant (PRIMA; Pixium Vision, Paris, France) in which pixels convert images projected from video glasses using near-infrared light into electric current to stimulate the nearby inner retinal neurons.

Design: We carried out a first-in-human clinical trial to test the safety and efficacy of the prosthesis in patients with geographic atrophy (ClinicalTrials.gov identifier, NCT03333954).

Participants: Five patients with geographic atrophy zone of at least 3 optic disc diameters, no foveal light perception, and best-corrected visual acuity of 20/400 to 20/1000 in the worse-seeing study eye.

Methods: The 2-mm wide, 30-μm thick chip, containing 378 pixels (each 100 μm in diameter), was implanted subretinally in the area of atrophy (absolute scotoma).

Main outcome measures: Anatomic outcomes were assessed with fundus photography and OCT for up to 12 months of follow-up. Prosthetic vision was assessed by mapping light perception, bar orientation, letter recognition, and Landolt C acuity.

Results: In all patients, the prosthesis was implanted successfully under the macula, although in 2 patients, it was implanted in unintended locations: within the choroid and off center by 2 mm. All 5 patients could perceive white-yellow prosthetic visual patterns with adjustable brightness in the previous scotomata. The 3 with optimal placement of the implant demonstrated prosthetic acuity of 20/460 to 20/550, and the patient with the off-center implant demonstrated 20/800 acuity. Residual natural acuity did not decrease after implantation in any patient.

Conclusions: Implantation of the PRIMA did not decrease the residual natural acuity, and it restored visual sensitivity in the former scotoma in each of the 5 patients. In 3 patients with the proper placement of the chip, prosthetic visual acuity was only 10% to 30% less than the level expected from the pixel pitch (20/420). Therefore, the use of optical or electronic magnification in the glasses as well as smaller pixels in future implants may improve visual acuity even further.

Figure 1.

System diagram of the photovoltaic retinal prosthesis, including camera integrated into augmented reality-like video glasses, with the processed image projected onto the retina using pulsed NIR light. Subretinal wireless photovoltaic array converts pulsed light into pulsed electric current in each pixel to stimulate the adjacent inner retinal neurons. Each pixel includes two diodes (1 and 2), connected in series between the active (3) and return (4) electrodes. Scale bar is 50 μm.

Figure 2.

Fundus photos and OCTs taken along the green line, with two implants in unintended locations: (A) in the choroid in patient #1; (B) in the periphery of the macula in patient #4. Scale bars are 200 μm. Yellow dash line indicates the back side of the implant. White lines underneath the implant are the OCT reflections. Images obtained during the 6-weeks to 6-months post-op visits.

Figure 3.

Fundus photos and OCTs with three implants in intended locations: (A) patient #2; (B) patient #3; (C) patient #5. Images obtained during the 6-weeks to 6-months post-op visits.

Figure 4.

A) Opaque video glasses with an integrated camera (white arrow) used in the feasibility study. B) Letter recognition and reading tests with one of the subjects, using the camera mode.