Optical energy transfer for intraocular microsystems studied in rabbits
Background: The development of a visual prosthesis aims to restore partial vision in patients with diseases which lead to total photoreceptor loss. The wireless power supply for a retinal implant may be realized with electromagnetic induction or with optical energy transfer. The present study investigates the feasibility of a photovoltaic power generation in the intraocular lens (IOL) part of an epiretinal implant for long-term tests in rabbits. Methods: IOLs containing an array of photovoltaic cells (PVC) and a light-emitting diode (LED) were implanted into the capsular bag after phacoemulsification in three chinchilla rabbits. Optical energy transfer was established with an infrared laser beam at 850 nm wavelength. Lighting up of the LED proved the functioning of the PVC array. The maximum duration of in vivo functioning of the implant was determined by regular tests involving laser beam application. The explanted microsystems were technically analyzed. Tissues of both eyes underwent routine histological examinations. Results: The lifespan of the microsystems ranged from 14 days to more than 7 months. Final malfunction was caused by PVC defects or by defective contacts between PVC and LED that may originate from the low adhesive strength between the silicone cover and the underlying electronic components. The histological examination showed no alterations of the retinal structure in the treated eyes. Conclusions: The power supply for intraocular microsystems by an array of photovoltaic cells was proven to be feasible in long-term tests in rabbits. An essential prerequisite for a future device is hermetic coating of the electronics.