A 44 channel suprachoroidal retinal prosthesis : surgical approach, safety and stability.

Abstract

Purpose : The success of our prototype clinical trial (NCT01603576) of a suprachoroidal retinal prosthesis lead us to develop a 44 channel fully implantable device, 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 at weekly intervals. The translation and rotation of the array relative to baseline (1 week post-implantation) was calculated at 10 weeks post-implantation for all four patients, and also at 25 weeks post-implantation for P1 and P2.

Results : The surgical procedures took between 204 and 260 minutes and were uncomplicated. At the completion of surgery, impedance testing showed in all patients, all electrodes were functional. Post operative recovery was uneventful. Fundus imaging and OCT imaging confirmed the device position and the absence of retinal trauma. Fundus imaging showed movement only in P3.
OCT imaging showed some movement of the device and for P1, P2, and P3, movement was primarily rotational, while for P4 movement was primarily translational.
P1 - 10 weeks: 1.5°rotation clockwise, 19μm translation nasally; 25 weeks: 3.3° rotation clockwise, 52μm translation temporally. P2 - 10 weeks: 3.1° rotation clockwise, 38μm translation temporally; 25 weeks: 4.3° rotation clockwise, 4μm translation nasally. P3 – 10 weeks: 13° rotation anticlockwise, 112μm translation temporally. P4 – 10 weeks: 0.8° rotation anticlockwise 252μm translation temporally.

Conclusions : A 44 channel retinal prosthesis can be safely implanted in the suprachoroidal space. Over three – six months of follow-up clinical findings, fundus photography and OCT imaging confirm safety and stability of the approach with no serious adverse events and only slight movement on OCT imaging, which can be either rotational or translational or both. Only P3 had movement had significant movement in both dimensions.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.