Abstract
Purpose :
To evaluate the spatial resolution of an electrode array for retinal prosthesis by suprachoroidal–transretinal stimulation (STS), we recorded the single-unit activities of relay cells in the lateral geniculate nucleus (LGN).
Methods :
Implantation surgeries were performed in cats (n = 4) under general anesthesia. The electrode array was chronically implanted into the scleral pocket of eyes. The electrode array had the same specifications as that used in the 2nd generation device of STS retinal prosthesis. This electrode array comprised 49 bullet-shaped electrodes that were 0.5 mm in diameter and 0.3 mm in height. The center-to-center distance of the electrodes was 0.75 mm. Under general anesthesia, acute experiments for the evaluation of spatial resolution of the electrode array were performed in 2–4 weeks after the implantation surgeries. The electrode position was identified by optical coherence tomography. Charge-balanced biphasic pulses were applied (pulse duration, 0.5 mm; current intensity, 0.1–1.0 mA) to the retina via each electrode independently. Stimulating trials were repeated 10 or 40 times, and response probabilities of single-unit activities in LGN relay neurons were analyzed. Their receptive fields were identified by visual stimulation, and the relationship between response probabilities and distances from the center of the receptive fields to the stimulating sites were evaluated.
Results :
The response probabilities decreased as the distance between the stimulating site and center of its receptive field increased. With 0.5 mA of stimulus intensity, the responsive area exhibiting a response probability of more than 50% was identified within a range of 1 mm from the stimulating site.
Conclusions :
These findings demonstrate that this electrode array is able to achieve localized stimulation. Moreover, spatial resolution by the STS approach appears to be acceptable, although the distance between the electrode and retina in this approach is larger than that in epi- or sub-retinal approaches.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.