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Photovoltaic Replacement of Photoreceptors in Geographic Atrophy

D. Palanker1, M.B. Bhuckory1, Z. Chen1, B. Wang1, T. Huang1, T. Kamins1, Y. Le Mer2, R. Hornig3, G. Buc3, M. Deterre3, S. Mohand-Said4, J.A. Sahel2,5
1 Department of Ophthalmology and Hansen Experimental Physics Laboratory, Stanford University, CA
2 Fondation Ophtalmologique A. de Rothschild, Paris, France
3 Pixium Vision, Paris, France
4 Clinical Investigations Center, Quinze-Vingts National Eye Hospital, Paris, France
5 Ophthalmology, University of Pittsburgh School of Medicine, PA

Purpose: To evaluate structural integration of the photovoltaic subretinal implant and its functional performance for restoration of central vision in patients with geographic atrophy.

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 vision. The wireless photovoltaic chip (PRIMA, Pixium Vision) is 2x2mm in size, 30µm in thickness, containing 378 pixels of 100µm in width. The subretinal prosthesis is activated by video glasses containing a camera and near-infrared projector. Each pixel in the implant converts pulsed near-infrared light (880nm) projected from video glasses into electric current to stimulate the nearby neurons in the inner nuclear layer of the retina. Anatomy of the chip integration with the retina was assessed with OCT, fundus photography and FA. Prosthetic vision was assessed using Landolt C test and letter recognition.

Results: In all 5 patients, chip implanted under the macula remains stable and functional, with a follow-up exceeding now 18-24 months in all patients. No decrease in natural eccentric visual acuity was observed in any of the patients. All 5 patients perceive white-yellow patterns with adjustable brightness, in retinotopically correct locations within previous scotomata. All 4 patients with subretinal placement of the chip achieved letter acuity in the range of 20/460 - 20/550, close to the sampling limit of resolution for this pixel size (20/420). In the second phase of the trial, patients started using transparent augmented-reality glasses, and demonstrated simultaneous perception of the peripheral natural and the central prosthetic vision. Adjustable zoom on new video glasses significantly increased the equivalent prosthetic acuity - up to 20/63.

Conclusions: Wireless chip PRIMA implanted under the atrophic macula in patients with geographic atrophy remains stable and functional during the 24 months of follow-up. It did not reduce the natural residual visual acuity in any of the patients. The implant provides central visual perception with acuity closely matching the pixel size of the photovoltaic array. Video glasses with optical or electronic zoom provide significantly higher resolution. For a broad acceptance of this technology by patients with geographic atrophy, visual acuity should exceed 20/100, which requires pixels smaller than 25µm. I will present a 3-dimensional electro-neural interface scalable to cellular dimensions and discuss the outlook and challenges for future developments.

Financial disclosures: DP: Pixium Vision - Consultant (C) and Patents (P); YLM: Pixium Vision (C); RH: Pixium Vision - Employment (E); GB: Pixium Vision (E); MD: Pixium Vision (E); JS: Pixium Vision - Personal Financial Interest (I)

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