Feasibility of 2nd Generation STS Retinal Prosthesis with 49 Channel Electrode Array in Dogs

Abstract

 

Purpose

 

We have demonstrated that suprachoroidal transretinal stimulation (STS) allowed 2 patients with advanced retinitis pigmentosa resolve to white bar targets. We have developed a 2nd generation STS system with a 49 channel electrode array, and the purpose of this study was to determine the feasibility of this new electrode array to be used as a retinal prosthesis.

 

Methods

 

To test the feasibility, we implanted an internal coil, a decoder, a multiplexer, and the 49 channel platinum electrode array (Fig. 1) in two dogs. The stimulating electrodes were implanted in the upper-temporal quadrant (dog 1) or lower temporal quadrant (dog 2). The return electrode was passed through the pars plana and implanted in the lower temporal (dog 1) or the upper nasal (dog 2) quadrant of the vitreous. The internal coil and the decoder were implanted under the fascia of the temporal muscle. Wires from the multiplexer and the return electrode were connected to the decoder. At the end of the surgery, internal devices were examined by connecting the external coil and delivering electrical pulses. The surface of the electrodes was processed by a femto-second laser to increase the charge injection capability. The electrical stimulating pulses consisted of cathodic-first biphasic pulses (duration, 0.5 msec; frequency, 20 Hz; interpulse delay, 0.5 ms; number of pulses, 20) and they were applied sequentially to each electrode with a delay of 0.45 ms.

 

Results

 

All electrodes were functioning at the end of surgery in both dogs. One month after the surgery, the fundus photographs and fluorescein angiograms showed no retinal damage in dog 1. Corneal artifacts elicited by the electrode array were recorded indicating that the electrodes were functioning.

 

Conclusions

 

Our results indicate that the 2nd generation STS retinal prosthesis is feasible and can be considered for clinical use.

 

 

Keywords: 607 nanotechnology • 696 retinal degenerations: hereditary • 762 vitreoretinal surgery