Safety Assessment of Chronic Suprachoroidal-Transretinal Stimulation in Normal Rabbits by the Femtosecond Laser-induced Porous Electrodes

Abstract

 

Purpose

 

We have proposed the ballet-shaped platinum(Pt) electrodes with Femtosecond Laser-induced Porous surface(FLiP) [Terasawa et. al., Invest Ophthalmol Vis Sci 2012;53: E-Abstract 5538]. 24-weeks in vivo chronic stimulation studies were conducted to assess the safety of Suprachoroidal-Transretinal Stimulation(STS) with abovementioned electrodes.

 

Methods

 

An electrode array with two porous electrodes was developed for this study(Fig.1). The diameter and height of an electrode were 0.5mm and 0.3mm respectively. Femtosecond laser pulses were applied onto the surfaces of bullet-shaped electrodes to form pores. The electrode array was inserted into a scleral flap of Japanese white rabbits. Charge balanced cathodic-first biphasic pulses with 1.5mA amplitude and 0.5ms width at repetition frequency of 50Hz were applied to one of two electrodes on the array for 8 hours per day for 24 weeks. Examinations including fundus photography, optical coherence tomography(OCT), electrically evoked potentials(EEPs) and histological evaluation were performed to detect tissue damage. Explanted stimulation electrodes were observed with scanning electron microscope(SEM) to compare with images obtained before implantation. All procedures conformed to the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research.

 

Results

 

No obvious injuries were observed in the all examination(Fig. 2). The EEP responses were observed after 24-weeks chronic stimulation. No sign of degradation was observed in the SEM of explanted electrodes.

 

Conclusions

 

We succeeded in confirming the safety of chronic STS with the FLiP electrodes. Additionally the electrodes showed enough reliability and biocompatibility for chronic stimulation in vivo.

 

 

Keywords: 688 retina