Feasibility of Semi-chronically Implanted Retinal Prosthesis by Suprachoroidal-Transretinal Stimulation in Patients with Retinitis Pigmentosa

Abstract

 

Purpose:

 

To examine the safety and effectiveness of a retinal prosthesis using suprachoroidal-transretinal stimulation (STS) that is implanted semi-chronically in two patients with advanced retinitis pigmentosa (RP).

 

Methods:

 

Two eyes of 2 patients with advanced RP had a retinal prosthesis implanted in a sclera pocket of one eye. The visual acuity of both eyes before the implantation was bare light perception. The internal devices of the STS were implanted under the skin on the temporal side of the head, and the 49 channel electrode array was implanted in the scleral pocket from lower-temporal side. Biphasic electrical pulses (duration, 0.5 ms; frequency, 20 Hz) were delivered through 9 active electrodes. The position of phosphene was mapped on a board using currents <1 mA. Behavioral tasks were used to determine the functioning of the prosthesis.

 

Results:

 

The surgery was completed without a retinal detachment and retinal/vitreous hemorrhage. The implanted STS system remained functional for the 4 weeks test period. Phosphenes were elicited by currents delivered through 6 electrodes in Patient 1 and in 4 electrodes in Patient 2. The position of phosphene was recorded upper-nasal area, which was consistent with the position of electrodes. The success of discriminating 2 bars was beyond the chance level in both patients. In Patient 2, the success of a grasping task was better than the chance level (P<0.05) and the success rate of the identification of the white bar on a touch panel increased with repeated testing.

 

Conclusions:

 

Semi-chronic implantation of a microelectrode-STS system showed that it was safe and remained functional for at least 4 weeks in two patients with advanced RP.  

 

Clinical Trial:

 

UMIN, R000002690

 

Keywords: clinical (human) or epidemiologic studies: systems/equipment/techniques • low vision • retinitis