Subretinal Visual Prosthetic Devices in Blind Patients. Modifications in Transchoroidal Surgery and Long Term Follow Up in the First 12 Patients

Abstract

Purpose: : Active subretinal visual prostheses require a transchoroidal implantation due to the necessary connection to extraocular structures for energy supply . A safe surgical transchoroidal procedure for a subretinal access was developed, modified and sucessfully applied in humans.

Methods: : The subretinal implant consisted of a stimulation chip with 1500 electrodes on a polyimide film. The energy supply for the stimulation was delivered via a retroauricular plug transdermal by a cable and transchoroidal by a polyimide film with supply lines.12 legally blind RP patients were included in the study and 11 were implanted with subretinal active prosthetic device via a transchoroidal access. Subretinal stimulation experiments could be carried out successfully in chronic subretinal implanted patients . Each electrode on the chip was controlled by light stimulating a neighbouring photo diode connected to a subretinal amplifier. According to protocol implants had to be removed from the eye after 30 days (8) or 3 month (3). Radiodiathermy with precise adjusted parameters allowed to penetrate the choroid without any bleeding. Specially developed guiding foils were used to support implantation. The design of the implant was impoved according surgical requirements.

Results: : Implantation was successfully performed in all patients with consecutive stimulation experiments demonstrating unique visual results in blind patients. Adverse events were not observed. The design modification of the implants and the guiding tools simplified the complex surgical maneuvers. One patient refused explantation. This patient was monitored for 4 years.

Conclusions: : The newly developed and modified transchoroidal implantation and explantation procedure was successfully established in humans. This procedure enables a safe subretinal implantation of large scale electronic subretinal prostheses in the macular region. This was the basis for successful stimulation experiments with unique results. Making this vision usable in every day life is focus of further developments.

Clinical Trial: : www.clinicaltrials.gov NCT00515814

Keywords: retina • vitreoretinal surgery