An update on visual prosthesis

Abstract

Purpose: To review the available evidence on the different retinal and visual prostheses for patients with retinitis pigmentosa and new implants for other indications including dry age-related macular degeneration.

Methods: The PubMed, GoogleScholar, ScienceDirect, and ClinicalTrials databases were the main resources used to conduct the medical literature search. An extensive search was performed to identify relevant articles concerning the worldwide advances in retinal prosthesis, clinical trials, status of devices and potential future directions up to December 2022.

Results: Thirteen devices were found to be current and were ordered by stimulation location. Six have active clinical trials. Four have been discontinued, including the Alpha IMS, Alpha AMS, IRIS II, and ARGUS II which had FDA and CE mark approval. Future directions will be presented in the review.

Conclusion: This review provides an update of retinal prosthetic devices, both current and discontinued. While some devices have achieved visual perception in animals and/or humans, the main issues impeding the commercialization of these devices include: increased length of time to observe outcomes, difficulties in finding validated meaures for use in studies, unknown long-term effects, lack of funding, and a low amount of patients simultaneously diagnosed with RP lacking other comorbid conditions. The ARGUS II did get FDA and CE mark approval so it was deemed safe and also effective. However, the company became more focused on a visual cortical implant. Future efforts are headed towards more biocompatible, safe, and efficacious devices.

Keywords: Artificial vision; Retinal prostheses; Retinitis pigmentosa; Stimulation; Visual prostheses.

Fig. 1

RP is a group of genetic progressive diseases, with an estimated prevalence of 1 in 4000 in the United States, that leads to total blindness. Though RP can be caused by mutations in any of over 190 genes, all lead to degeneration of the photoreceptor layer of the retina. The relative preservation of inner retina has led to efforts to develop retinal prostheses to stimulate residual surviving tissue. Left: the classic clinical triad of RP is arteriolar attenuation, retinal pigmentary changes (could be either hypopigmentation and/or hyperpigmentation in form of bone-spicule and pigment clumpings), and waxy disc pallor. Middle cartoon: normal eye. Right cartoon: eye with RP

Fig. 2

Internal component of the IMIE 256 (Modified and reprinted with permission from Xu H, Humayun MS, et al. First Human Results With the 256 Channel Intelligent Micro Implant Eye (IMIE 256). Transl Vis Sci Technol. 2021 Aug 12;10(10):14.)

Fig. 3

External component of the IMIE 256 (Modified and reprinted with permission from Xu H, Humayun MS, et al. First Human Results With the 256 Channel Intelligent Micro Implant Eye (IMIE 256). Transl Vis Sci Technol. 2021 Aug 12;10(10):14.)

Fig. 4

PRIMA Device (Courtesy of PIXIUM VISION, Paris, France)

Fig. 5

A: Photograph showing the opaque video glasses with an integrated camera (white arrow) used in the feasibility study. B: Photograph showing letter recognition and reading tests with one of the patients, using the camera mode (Reprinted with permission from Palanker D, Le Mer Y, Mohand-Said S, Muqit M, Sahel JA. Photovoltaic Restoration of Central Vision in Atrophic Age-Related Macular Degeneration. Ophthalmology. 2020 Aug;127(8):1097–1104.)

Fig. 6

System diagram showing the photovoltaic retinal prosthesis, including the camera integrated into augmented reality-like video glasses, with the processed image projected onto the retina using pulsed near-infrared (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 2 diodes (1 and 2), connected in series between the active (3) and return (4) electrodes. Scale bar 1⁄4 50 mm (Reprinted with permission from Palanker D, Le Mer Y, Mohand-Said S, Muqit M, Sahel JA. Photovoltaic Restoration of Central Vision in Atrophic Age-Related Macular Degeneration. Ophthalmology. 2020 Aug;127(8):1097–1104.)

Fig. 7

Fundus photographs and OCT images with 3 implants in intended locations: A: patient 2, B: patient 3, and C: patient 5. Images were obtained during the 6-week to postoperative visits (Reprinted with permission from Palanker D, Le Mer Y, Mohand-Said S, Muqit M, Sahel JA. Photovoltaic Restoration of Central Vision in Atrophic Age-Related Macular Degeneration. Ophthalmology. 2020 Aug;127(8):1097–1104.)

Fig. 8

The Generation 2 by Bionic Vision Australia (BVA) A: Internal components B: External components (Reprinted with permission from Petoe MA, Titchener SA, Kolic M, Kentler WG, Abbott CJ, Nayagam DAX, et al. A Second-Generation (44-Channel) Suprachoroidal Retinal Prosthesis: Interim Clinical Trial Results. Transl Vis Sci Technol. 2021;10(10):12.)

Fig. 9

The ORION Visual Cortical Prosthetics system. External components (Left). It is placed on the medial occipital lobe over V1 and V2 (Right) (Courtesy of Gislin Dagnelie, Ph.D.)