A 44 channel suprachoroidal retinal prosthesis: laboratory based visual function and functional vision outcomes.

Abstract

Purpose : The 44 channel (44Ch) suprachoroidal retinal prosthesis is a second-generation bionic eye implant that follows on from a proof of concept study conducted between 2012 and 2014. The 44Ch implant is designed to provide artificial vision (phosphenes) to recipients with end-stage retinitis pigmentosa (RP). We aimed to compare the performance of visual function and functional vision tasks at pre-implantation and post device activation.

Methods : The 44Ch suprachoroidal retinal prosthesis was unilaterally implanted in 4 participants with advanced RP, age range 39 to 66 years, between February and August 2018. After a 16-week period of vision rehabilitation training, participants were assessed on three laboratory-based visual function tasks: moving bar (MB), square localisation (SL) and grating acuity (GA), followed by three functional vision tasks: table-top search (TTS), doorway detection (DWD) and obstacle avoidance (OA). Assessment time points were pre-implantation and from post-device activation at weeks 17 (W17), W20, W32, W44, W56 and W68. Data was pooled across all 4 participants and performance was compared between device on and off.

Results : With device on, three of the four participants could discriminate MB speeds ranging from 7 to 30 degrees per second. Average pointing error for all four participants, across all visits on SL, was 10.3 ± 3.3° (device on) versus 27.7 ± 8.7° (device off), p < 0.001. Two of the four participants had measurable GA of 0.033 cycles-per-degree. On average, the device improved participants’ ability to locate objects on the TTS, detect and touch the doorway on DWD task and detect and avoid more obstacles during OA, at all-time points post-activation (p<0.04), compared to device off.

Conclusions : The 44Ch second generation suprachoroidal implant improved overall performance on both laboratory-based visual function and functional vision tasks, compared to device off. The device shows the capability to provide visual sensory information, to aid detection of obstacles and improve accuracy when reaching for an object, for people with profound vision loss due to RP.

This is a 2021 ARVO Annual Meeting abstract.