The influence of stimulating electrode conditions on electrically evoked potentials and resistance in suprachoroidal transretinal stimulation

Purpose To determine the influence of stimulating electrode conditions on the amplitudes and latencies of electrically evoked potentials (EEPs) and the resistance at the electrode–tissue interface in the suprachoroidal transretinal stimulation (STS) system. Study design Experimental study. Methods A scleral pocket (3 × 5 mm) was created just over the visual streak in anesthetized pigmented rabbits (weight, 1.9-2.7 kg), and STS stimulating electrodes were implanted into the pocket. Measurements were obtained with stimulating electrodes of different lengths (0.3 or 0.5 mm) and different surface characteristics (smooth or porous). EEPs elicited with a fixed current under each set of electrode conditions were recorded; three measurement sessions were performed for each rabbit. The resistance at each electrode–tissue interface was measured. Results The latencies and amplitudes of the EEPs did not differ significantly with changes in the height and surface characteristics of the stimulating electrodes, but the resistances at the electrode–tissue interface differed significantly (P = 0.001; the resistance values for the 0.3-mm-long electrode with a porous surface was 5.24 ± 0.67 kΩ and with the 0.3- and 0.5-mm-long electrodes with smooth surfaces were 7.63 ± 0.12 kΩ and 6.77 ± 0.20 kΩ). Conclusion Being shorter did not affect the EEPs of the stimulating electrodes with a porous surface while decreasing the resistance at the electrode–tissue interface.