Subretinal Chronic Active Multi–Electrode Arrays in Blind Patients: Fundus Appearance, Optical Coherence Tomography and Angiography

Abstract

Purpose: : Monitoring of biostability and biocompatibility of a subretinal implant, consisting of an active amplifying multiphotodiode array (chip) with an additional 4x4 array of electrodes for direct stimulation (DS).

Methods: : The chip and DS electrodes are arranged adjacent on a polyimide substrate, carrying also several conductor paths. The device was implanted next to the foveal rim of two blind retinitis pigmentosa patients. The subretinal polyimide stripe leaves the eye bulb between equator and pars plana through the choroid and a scleral flap. Before and after implantation fundus photography, OCT scan and fluorescein angiography was performed regularly during four weeks of the study period.

Results: : The implant was well tolerated in both subjects. One patient showed fully attached retina immediately after surgery and at all further visits. In the second patient we observed subretinal liquid at the site of the implant that resolved within two weeks. OCT examinations turned out to be very valuable assessing the subretinal alignment of the device and the stability of its position in relation to the retina. OCT scans demonstrated small intraretinal densifications that corresponded in fundoscopy to well demarcated changes at the edges of the chip. After explantation in one patient, which took place according to study plan, the retina showed only minor changes at the implantation site. Angiography showed well preserved retinal capillaries at the implantation site. During the study period dilatation of retinal vessels was observed angiographically above the device. In one patient very mild early stage fluorescein staining was observed next to one dilated vessel.

Conclusions: : According to fundus examination, OCT scan and angiography the subretinal implants were well tolerated by the surrounding tissue during an observation time of four weeks so far.

Keywords: retina • retinal degenerations: hereditary • clinical (human) or epidemiologic studies: systems/equipment/techniques