title: Characteristics of retinal reflectance changes induced by transcorneal electrical stimulation in cat eyes.
abstract: Transcorneal electrical stimulation (TES) activates retinal neurons leading to visual sensations. How the retinal cells are activated by TES has not been definitively determined. Investigating the reflectance changes of the retina is an established technique and has been used to determine the mechanism of retinal activation. The purpose of this study was to evaluate the reflectance changes elicited by TES in cat eyes. Eight eyes of Eight cats were studied under general anesthesia. Biphasic electrical pulses were delivered transcornealy. The fundus images observed with near-infrared light (800-880 nm) were recorded every 25 ms for 26 s. To improve the signal-to-noise ratio, the images of 10 consecutive recordings were averaged. Two-dimensional topographic maps of the reflective changes were constructed by subtracting images before from those after the TES. The effects of different stimulus parameters, e.g., current intensity, pulse duration, frequency, and stimulus duration, on the reflective changes were studied. Our results showed that after TES, the reflective changes appeared on the retinal vessels and optic disc. The intensity of reflectance changes increased as the current intensity, pulse duration, and stimulation duration increased (P<0.05 for all). The maximum intensity of the reflective change was obtained when the stimulus frequency was 20 Hz. The time course of the reflectance changes was also altered by the stimulation parameters. The response started earlier and returned to the baseline later with higher current intensities, longer pulse durations, but the time of the peak of the response was not changed. These results showed that the reflective changes were due to the activation of retinal neurons by TES and might involve the vascular changes induced by an activation of the retinal neurons.
authors.affiliation: Department of Applied Visual Science, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Morimoto
authors.affiliation: Department of Applied Visual Science, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kanda
authors.affiliation: Department of Integrative Physiology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Tomomitsu
authors.initials: T
authors.lastname: Miyoshi
authors.affiliation: Research Institute, Topcon Corporation, Itabashi-ku, Tokyo, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Hirohara
authors.affiliation: Innovative Research Initiatives, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Mihashi
authors.affiliation: Department of Applied Visual Science, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Kitaguchi
authors.affiliation: Department of Ophthalmology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Kohji
authors.initials: K
authors.lastname: Nishida
authors.affiliation: Department of Applied Visual Science, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Fujikado
mesh_terms: D000818:Animals; D002415:Cats; D003315:Cornea / Q000502:physiology*; D004558:Electric Stimulation; D055724:Electrophysiological Phenomena; D005260:Female; D005654:Fundus Oculi; D008297:Male; D009799:Ocular Physiological Phenomena; D009897:Optic Chiasm / Q000502:physiology; D010775:Photic Stimulation; D012160:Retina / Q000502:physiology*