Positioning of Electronic Subretinal Implants in Blind Retinitis Pigmentosa Patients Through Multimodal Assessment of Retinal Structures

Abstract

PURPOSE. To optimize methods for positioning subretinal visual implants, customizing their cable length, guiding them to the predetermined retinal position, and evaluating their performance.METHODS. Ten eyes of 10 patients (6 male, 4 female, mean age 46.4 years) were investigated before implantation of a subretinal visual implant. The structural characteristics of the retina as well as the ocular dimensions were determined. Topographic images of the prospective implantation site were subdivided into grids of squares. Each square received a weighted score for suitability. The sum of the scores was calculated, and the region with the highest score was chosen for the implant. In each case, the implant's power supply cable length was calculated by means of magnetic resonance imaging. The planned and achieved positions before and after implantation were compared. RESULTS.The mean light sensitivity ratio between the area actually covered by the chip and that of the planned position was 90.8% with an SD of 11.4%. In two cases with almost perfect positioning, the computed ratio was 100%. Measurements showed that to achieve a 95% sensitivity rate the difference between the planned and achieved chip position must be less than 1.7 mm. Preoperative calculations of the intraocular cable length proved accurate in all cases.CONCLUSIONS. Preoperative evaluation of retinal structures and eye morphology is useful for guiding a retinal implant to the designated area. It is a meaningful tool for planning and performing retinal chip implantation, and it optimizes personalized implantation. (ClinicalTrials.gov numbers, NCT00515814, NCT01024803.) (Invest Ophthalmol Vis Sci.

Retinal implants: a systematic review: Table 1

“…Each of the 1500 pixels consists of a light-sensing photodiode that responds to ambient light entering the eye. Signals are amplified and transferred to local electrodes, stimulating the geographic region corresponding to phosphene detection 8. While image acquisition is solely intraocular, a cable connects the implant to a subdermal power control unit, which charges wirelessly through a handheld control unit that enables light-sensitivity adjustment 6 10.…”

“…These trends underscore the need for a systematic review that provides a neutral third-party analysis of current prostheses using a priori criteria of success. To this end, we evaluate herein the state of current retinal prostheses with particular emphasis on their clinical availability,1 vision restoration8 and long-term biocompatibility9 in patients with vision loss due to degenerative retinopathy.…”

Subretinal Visual Implant Alpha IMS – Clinical trial interim report

“…Before surgery, the desired subfoveal position is determined (Kusnyerik et al, 2012). However, due to adhesions, foveal thinning, the curvature of the eye, and the length and flexibility of the polyimide foil, it is not always possible to precisely position the chip.…”

Retinal prostheses in degenerative retinal diseases

“…Signals are amplified and transferred to local electrodes, stimulating the geographic region corresponding to phosphene detection. 25 While image acquisition is solely intraocular, a cable connecting the implant to a subdermal power control unit, which charges wirelessly through a handheld control unit, enables light-sensitivity adjustment. 26,27 Early models with a transdermal power supply limited the study to 126 days.…”