Changes in Microchip Position after Implantation of a Subretinal Vision Prosthesis in Humans

Abstract

Purpose : Retinal prosthetic devices have been developed to partially restore very-low-vision in legally blind patients with end-stage hereditary retinal dystrophies. Subretinal implants, unlike epiretinal implants, are not attached to the retina by a tack. The aim of this study was to assess and analyze possible changes over time in the subretinal position of the RETINA IMPLANT Alpha IMS and AMS (ClinicalTrials.gov NCT01024803).

Methods : Imaging studies were performed on fundus photographs using GIMP (Version 2.8.14). All photographs of the implanted eye were scaled and aligned. If no obvious microchip displacement occurred between any of the visits, the implant was considered stable. In those eyes, in which displacement occurred, landmarks were chosen and distances between landmarks were measured to then calculate the displacement of the microchip using a transformation matrix for rotational and translational movements. Analyses were performed using MATLAB 8.6 (The MathWorks Inc., Natick, MA).

Results : Of the 27 datasets with the Alpha IMS device, 12 (44%) remained stable without displacement of the microchip relative to the optic disc and the major blood vessels, whereas in 15 (56%), displacement occurred. The mean ± SD displacement in those 15 eyes was 0.66 ± 0.35 mm (range, 0.24 - 1.67 mm, Fig. 1). Of the 8 datasets with the Alpha AMS device, 1 (13%) remained stable without displacement of the microchip relative to the optic disc and the major blood vessels, whereas in 7 (87%), displacement occurred. The mean ± SD displacement in those 7 eyes was 0.66 ± 0.26 mm (range, 0.32 - 0.97 mm, Fig. 1).

Conclusions : In this study, we assessed postoperative changes in the position of the RETINA IMPLANT Alpha IMS and AMS in 36 eyes, which constitutes for a rather large cohort given the number of patients in which RETINA IMPLANT Alpha IMS or AMS surgery has been performed until now. We show that the subretinal position of the visual implant can change after implantation in some patients, but the overall mean displacement of the chip remains minor.

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

 

Fig. 1 Mean movement (mm) of the RETINA IMPLANT Alpha IMS and AMS after implantation in those eyes, in which displacement occured (N = 15 for Alpha IMS and N = 7 for Alpha AMS). Note that there is no difference in the mean between the two cohorts (0.66 mm).