title: Threshold suprachoroidal-transretinal stimulation current resulting in retinal damage in rabbits.
abstract: The purpose of this study is to determine the threshold suprachoroidal-transretinal stimulation (STS) current that results in retinal damage in rabbits. Biphasic STS pulses (anodic first, frequency 20 Hz) were used to stimulate the retina of pigmented rabbits (n = 18) continuously for 1 h using a 100 microm diameter platinum wire electrode. The STS current that induced retinal damage after 1 h was determined by ophthalmoscopy or by fluorescein angiography (FA) independently. The effect of the pulse duration on the threshold current was investigated. Histological studies were performed after electrical stimulation experiments. The threshold for a safe current to the retina was 0.6 mA for a duration of 0.5 ms. The threshold for a safe charge increased approximately linearly with an increase of stimulus duration but the threshold for a safe current decreased logarithmically with an increase of duration. The threshold for a safe electrical energy remained almost constant for all durations. Histological examination showed severe retinal damage when the current exceeded the threshold, with more damage in the inner layers compared with the outer layers of the retina. The threshold for the safe current was higher than that reported for direct stimulation of neural tissues, suggesting that the STS method was safe and able to be used with a retinal prosthesis. Because the threshold for the safe charge was lower with shorter pulse durations, care should be taken using pulses of short durations.
authors.affiliation: Department of Applied Visual Science, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Nakauchi
authors.forename: Takashi
authors.initials: T
authors.lastname: Fujikado
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kanda
authors.forename: Shunji
authors.initials: S
authors.lastname: Kusaka
authors.forename: Motoki
authors.initials: M
authors.lastname: Ozawa
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Sakaguchi
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ikuno
authors.forename: Motohiro
authors.initials: M
authors.lastname: Kamei
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Tano
mesh_terms: D000818:Animals; D002829:Choroid / Q000293:injuries* / Q000473:pathology*; D004056:Differential Threshold; D004558:Electric Stimulation / Q000009:adverse effects*; D005131:Eye Injuries / Q000209:etiology / Q000473:pathology; D011817:Rabbits; D012160:Retina / Q000293:injuries* / Q000473:pathology*; D018570:Risk Assessment