Injectable, Self-opening, and Freestanding Retinal Prosthesis for Fighting Blindness

Purpose:In the past decade, retinal prostheses emerged as promising technology to restore a primitive, although clinically useful, form of vision. However, fighting blindness with retinal prostheses require challenges not yet achieved. From a clinical perspective, sight restoration requires to reach two main goals: enlarging the visual field of the patient and improving its visual acuity. From the engineering point of view, these needs demand the overcoming of two major issues: implanting a prosthesis (i) large enough to cover the retinal surface and (ii) embedding a high number of highly dense stimulatory elements. Our goal is the development of an injectable, self-opening, and freestanding retinal prosthesis restoring at least 40° of visual field, therefore covering at least a retinal surface of 12 mm in diameter. Moreover, the prosthesis must have a hemispherical shape in order to minimize the distance from the targeted cells over its entire surface, it should operate according to a photovoltaic stimulation principle and it must be injected trough a minimal scleral incision. Methods:Using solution processes and micro-fabrication techniques, we designed a retinal prosthesis based on polydimethylsiloxane (PDMS) as shell material, embedding photovoltaic pixels made of conjugated polymers. The prosthesis is shaped with a molding technique. Results:The prosthesis consists in a photovoltaic PDMS-interface, embedding 2345 organic stimulating pixels (100 µm and 150 µm in diameter, density 54.34 px/mm2) with a biomimetic distribution in an active area of 13 mm (44° of visual field). Our results indicate that those photovoltaic pixels can deliver up to 54.22±10.55 mA/cm2 and generate an electrode potential of 182.22±6.72 mV when illuminated with a pulse light of 10 ms, 32.47 µW/mm2, at 530 nm. Sample tested n = 20. Accelerated aging tests and experiments with explanted retinas are currently under evaluation. Conclusions:These preliminary results show the potential of organic photovoltaic technology in the fabrication of a retinal prosthesis with large surface area and high stimulation efficiency. The biocompatibility and mechanical compliance of the materials represent an additional step forward in building advanced photovoltaic retinal prostheses.