Transchoroidal Implantation of Active Subretinal Implants in Blind Patients: Experience With the New Surgical Implantation and Explantation Procedures in the First Six Patients

Abstract

Purpose:: The size of subretinal active visual prostheses positioned on polymide foils and their necessary connection to extraocular structures for energy supply requires a transchoroidal surgical implantation procedure. A safe surgical transchoroidal access to subretinal space is mandatory for a successful chronic implantation in patients.

Methods:: Six volunteer legally blind RP-patients were implanted with an electronic retinal prosthesis. The implant consisted of a light sensitive multielectrode array (3x3 mm) with 1500 photodiodes, amplifiers and electrodes on a polyimide foil and additional electrode array for direct stimulation with16 TiN electrodes. The microelectrode arrays were implanted subretinally via a transchoridal procedure near the temporal equator of the eye. Careful radiodiathermy with precise adjusted parameters allowed to penetrate the choroid without bleeding. A specially designed guiding foil was used as an implantation instrument. Silicone oil was used as a tamponade. The energy required for stimulation was delivered via a retroauricular plug by a transdermal cable and transchoroidally by a polyimide foil (1x0,1 mm) with supply lines. Thus subretinal stimulation experiments could be carried out successfully in chronically implanted patients for the first time. According to schedule the implants had to be removed after 30 days.

Results:: Implantation was successfully performed in 6 patients. No surgically induced adverse events (choroidal bleeding, retinal detachment, inflammation etc.) were observed during the surgical procedure or the follow up period of up to 14 months; the implants remained stable in all cases. 5 implants were explanted according to schedule approx. 30 days after implantation. One patient refused the explantation and kept the implant. This patient was closely monitored for 14 months and showed.

Conclusions:: The newly developed transchoroidal implantation and explantation procedure was successfully established in patients. This procedure allows for a safe chronic stable subretinal implantation and explantation of relatively large electronic prostheses. An exchange option of subretinal implants appears feasible if necessary and desired.

Keywords: vitreoretinal surgery • low vision