Objective: Retinal implants have the potential to restore some sight in patients with retinal degeneration. The PRIMA implant's novel design features simpler insertion and no transscleral cabling or extraocular components. This in vitro study investigated PRIMA's durability under real time and accelerated conditions and estimated the device's lifespan in vivo.
Approach: Two potential failure modes were examined: corrosion and overstimulation. Real-time aging was tested using implants immersed in balanced saline solution (BSS) at 37 °C, mimicking the intraocular environment. Accelerated aging was examined at 77 °C (Arrhenius theory). Confirmatory testing of acceleration factor was performed using different temperatures (37 °C-87 °C) and weakened implant coatings. The effect of repeated maximum stimulation was tested using a pulsed infrared laser (6x acceleration factor). Data were used to estimate device lifespan.
Main results: 175 implants were tested for up to 33 months. No corrosion or water ingress was observed after approximately 20 accelerated years. A pixel failure rate of 0.15% was recorded after 10 accelerated years' stimulation. The derived lifespan estimation for the PRIMA implant was 27.0 years with a reliability of 90% (95% confidence interval).
Significance: The PRIMA implant was found to be robust, with in vitro reliability of at least 10 years. The PRIMA implant shows durability and functionality for clinically relevant timespans under similar environmental conditions to the human eye. These results require in vivo confirmation.