OCT Characteristics Among Subjects Implanted with the Argus II Retinal Prosthesis System; the Argus II OCT Study Group

Abstract

Purpose : The Argus II retinal prosthesis system is the first FDA-approved epiretinal implant aimed to partially restore vision in patients with outer retinal dystrophy, most often retinitis pigmentosa. There is a paucity of data regarding changes in retinal anatomy after implantation. We performed a retrospective review of retinal images of Argus II recipients to evaluate the macular structure after implantation.

Methods : US and European surgical sites participating in the Post-market approval study were contacted for voluntary participation (all participating investigators will be listed as the Argus II OCT Study Group). Baseline demographics, fundus photographs and OCT images obtained preoperatively and 1, 3, 6, and 12 months after implantation were evaluated. Images were reviewed for macular edema, epiretinal membrane (ERM), optic nerve overlap as well as the distance of the array to the inner retinal surface. Frequency distributions were used to describe the data. Images that were deemed unreadable by two separate investigators were excluded.

Results : Among post-approval study investigators, 86% (n=24) agreed to participate. The patients were implanted between January 2014 and October 2016. Participants were 68% male with a mean age at time of implantation of 62.3 years (SD 10.9). ERM was not seen in any patients preoperatively and was seen in 50% at one year post-implant. Macular edema was absent in all patients preoperatively and was present in all available one-year images (100%). A portion of the electrode array overlapped the optic nerve in the majority of subjects, however, the overlap was usually limited to the plastic bumper without direct nerve-electrode contact. The mean distance from the central electrode to the internal limiting membrane was 182 microns.

Conclusions : Following Argus II retinal prosthesis implantation, macular edema and ERM formation commonly occurred. Some degree of array-optic nerve overlap was seen in most subjects, however, the electrodes were usually not in direct contact with the nerve. Future work will be done to evaluate the gap between the array and the inner retina and to correlate that distance with stimulation thresholds and impedance values. The ultimate goal is to gain knowledge that may be helpful for optimal device implantation and array modifications to maximize functionality.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.