A 44 Channel suprachoroidal retinal prosthesis : two year safety and stability results

Abstract

Purpose : The success of our prototype clinical trial (NCT01603576) of a suprachoroidal retinal prosthesis led us to develop a 44 channel fully implantable device with a transcutaneous receiver stimulator system, with the aim of providing visual information to profoundly visually impaired patients, allowing them to utilise this device at home.

Methods : Four patients (P1, P2, P3 and P4) with end-stage rod - cone dystrophy and perception of light visual acuity were implanted with a 44 channel electrode array in the suprachoroidal space during 2018 (NCT03406416). After recovery they commenced stimulation of the device in the psychophysics laboratory.
Post operative follow-up included clinical examination, fundus photography and optical coherence tomography (OCT) to assess surgical recovery and impact on the eye.
OCT imaging was used to track the retinotopic location of the leading edge of the implant. The translation and rotation of the array relative to baseline (1 week post-implantation) was calculated at 108 weeks post-implantation.
Primary outcome measure was safety as asessed by device related serious adverse events (SAEs), secondary measure efficacy as assessed by tests of visual function and functional vision.

Results : The surgical procedures were uncomplicated. At the completion of surgery, impedance testing showed in all electrodes were functional in all patients. Post operative recovery was uneventful . Fundus imaging and OCT imaging confirmed the position of the devices under the macula and the absence of retinal trauma.
No device related serious adverse events occurred during the two years of the study.
OCT imaging showed some minor movement of the device for all four patients. P3 had the most significant movement with 15 degrees of rotation at 108 weeks compared to baseline, however no functional changes were noted. Translational movement was minimal in all patients.

Conclusions : A 44 channel retinal prosthesis can be safely implanted in the suprachoroidal space, with no serious adverse events, device related or not, recorded for 4 patients. Over twenty four months of post operative follow-up clinical findings, fundus photography and OCT imaging confirm safety and stability of the suprachoroidal approach with only slight movement on OCT imaging, which is usually rotational. The devices were functional for the 24 months of the study and continue to be used in the home enviroment.

This is a 2021 ARVO Annual Meeting abstract.