Acute animal model for subretinal prosthesis implantation

Abstract

Purpose : Retinal prostheses are engineered photosensitve neurostimulators which have the potential to restore vision for blind patients. The engineered photosensor needs to be surgically implanted in an animal model for various optimizations before moving to clinical trials. We developed an “implant sandwich” subretinal surgical technique in an acute rabbit eye model with electrophysiology and optical topography.

Methods : Retinal prostheses, 3mm x 4 mm x 300 µm, was implanted subretinally into the right eyes of 7 New Zealand pigmented rabbits. Ab-externo trans-choroidal procedure was modified by creating an “implant sandwich” with 2 flexible glides on both sides of the prosthesis and introduced into the subretinal space directly under view of a surgical microscope. Ophthalmoscopic exams, fundus imaging, and OCT analysis were conducted to assess prosthesis positioning and to monitor the anatomical changes of the overlying retina over time. VEPs were recorded 24 hours after implantation to assess the health of the retina. Eyes were collected 2 weeks later for histopathology.

Results : Successful subretinal implantation into the visual streak area by using a sandwich technique was achieved in all rabbits(Fig.1). The retina overlying the sensor demonstrated layered structures on OCT and revealed excellent apposition from the next day on. The overlying retina showed progressive thinning from day 3 by OCT analysis(Fig.2). Post-operative VEP recordings demonstrated average N1 amplitude and latency was -61.5 μV and 38.2 ms. Average P2 amplitude and latency was 49.5 μV and 162.6 ms, which indicated that the retina remained responsive to bright light stimulation and tolerated the subretinal implantation surgery. Histology confirmed the findings on the OCT.

Conclusions : The “implant sandwich” technique works well for subretinal prosthesis implantation in rabbit eyes which can serve as an acute model to assess optimal engineering designs.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Fig.1 Sandwich assembling and surgical implanting

 

Fig.2 OCT monitoring of the overlying retina after implantation