Abstract
Purpose :
Retinal implants have the potential to restore some level of vision in patients with retinal degeneration. The PRIMA retinal implant’s novel design features simpler insertion and no transscleral cabling or extraocular implanted components. This study investigated PRIMA’s durability under in vitro real time and accelerated conditions and estimated the device’s lifespan in vivo.
Methods :
Two distinct failure mode tests were performed: corrosion and overstimulation. Corrosion testing was performed through real-time and accelerating aging. 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 with an acceleration factor of 14 as determined by a dedicated Arrhenius theory testing. Overstimulation testing consisted in repeating 24h a day maximum stimulation using a pulsed IR laser on implants in BSS at 37°C, with an acceleration factor of 6 compared to typical use. Visual inspections and electrical performances data from both tests were used to estimate device lifespan through a Weibull analysis. In vivo device lifetime data from preclinical and clinical trials was also considered.
Results :
175 implants were tested in vitro for up to 33 months: 68 implants underwent corrosion testing and 107 stimulation testing. 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, based on data of each tested pixel. The derived median lifespan estimation for the 378-pixel PRIMA implant – design currently used in clinical trial - was 27.0 years with a reliability of 90% (95% confidence interval). Additionally, in vivo data from pre-clinical study demonstrate an implant lifetime of at least 2 years in two non-human primates and 3 years in a third one, while current data from ongoing clinical trial show full implant functionality in all 5 patients after 18 to 24 months implantation.
Conclusions :
The PRIMA implant was found to be robust, with in vitro reliability of at least ten years with a high confidence level. Although these results require in vivo confirmation, currently available preclinical and clinical in vivo data is compatible with this conclusion.
This is a 2020 ARVO Annual Meeting abstract.