Results of the Preoperative Planning Procedure Before Subretinal Prosthesis Implantation in Humans

Abstract

Purpose: : Several concepts have attempted to produce useful visual sensation through implantation of electronic devices. Recently in the long-term clinical trial, the preoperative planning procedure was implemented to determine the optimal location on the fundus for surgical implantation of a subretinal microphotodiode-array (MPDA).

Methods: : Eye morphology and retinal structure of the eyeball was assessed in four subjects scheduled for MPDA implantation. Imaging techniques were used to topographically assess individual eye morphology, retinal structures and functions. Color fundus photographs, fluorescein angiography, OCT maps, and electrical phosphene thresholds were assessed, resulting in a concordant fundus map as guideline for the surgeon. An ellipsoid eye model was used to determine the optimal outcome parameters.

Results: : After identifying the optimal location with preoperative planning, better functional results were noted in patients. The parameters given to the surgeon proved to be precise and it was possible to attain the desired location with significantly less effort.After co-registration of image-sequences to assess stability of the implant in relation to the overlying retina only small movements (up to 100µm) were observed in three cases. In 1 patient a horizontal displacement of 1disc diameter was found.

Conclusions: : The preoperative evaluation provides a meaningful tool for planning the surgical implantation of a subretinal visual prosthesis and could be useful to other approaches as well (e.g. epiretinal and suprachoroidal prostheses). It is very important to accurately situate the prosthesis to stimulate living cells and not inert areas on the retina.

Clinical Trial: : www.clinicaltrials.gov NCT00515814

Keywords: retina • imaging/image analysis: clinical • computational modeling