An Overview On Transchoroidal Surgery For Subretinal Visual Prosthetic Devices On The First 20 Blind Rp-patients

Abstract

Purpose: : The power and signal transmission to a subretinal electronic chip requires a transchoroidal connection to external supply structures. A safe surgical transchoroidal procedure for a subretinal implantation of visual prosthetic devices was developed and successfully applied in blind retinitis pigmentosa (RP) patients. Long term results of this surgical procedure and their modifications are evaluated.

Methods: : Subretinal implants are composed of a stimulation chip with 1500 electrodes mounted on a polyimide film which serves as a transchoroidal connecting cable for power and signal transmission were implanted in 20 blind RP patients via a newly developed transchoroidal access. In the cable bound pilot study implants had to be removed from the eye after 30 day (n=8); in the subsequent main study wireless versions of the implants were designed to remain in patients . The role of radio diathermy with precisely adjusted parameters which allowed penetrating the choroid without any bleeding in conjunction with special guiding foils were investigated. Some aspects of implant design were changed during the study to meet surgical requirements. Surgery, stability of the placement and biocompatibility were evaluated.

Results: : Implantation was successfully performed in all patients. Thus unique visual abilities in blind patients were restored. The design modification of the implant and the guiding tools simplified the surgical manoeuvres. No retinal detachment or major displacement of the implant occurred. Inflammation or endophthalmitis was not observed. Explantation, relocation and exchange of the implant were carried out without any problem if necessary.

Conclusions: : The newly developed and modified transchoroidal implantation and explantation procedure was successfully established in RP-patients. This procedure enables a safe subretinal implantation of large scale electronic prostheses. Implant design modifications allowed relocation and exchange which provides additional chances for the patient to benefit from electronic implants even in case of exchange due to device failure.

Clinical Trial: : http://www.clinicaltrials.gov NCT00515814

Keywords: vitreoretinal surgery • degenerations/dystrophies • neuro-ophthalmology: cortical function/rehabilitation