title: Comparing retinal reflectance changes elicited by transcorneal electrical retinal stimulation with those of optic chiasma stimulation in cats.
abstract: OBJECTIVE
  To compare retinal reflectance changes (RCs) elicited by transcorneal electrical stimulation (TES) to those elicited by electrical stimulation of the optic chiasma (OX).
  
  
  METHODS
  Two eyes of two cats were studied under general anesthesia. Biphasic electrical pulses at 20 Hz were applied for 5 ms in TES, and monophasic pulses were applied for 50 μs at 100 Hz in OX stimulation. Fundus images observed with near-infrared light (800-880 nm) were recorded every 25 ms for 26 s, beginning 2 s before and ending 20 s after the electrical stimulation. To improve the signal-to-noise ratio, the images of ten consecutive recordings were averaged. Two-dimensional topographic maps of the RCs were constructed by subtracting images before the stimulation from those after the stimulation. The electrically evoked potentials (EEPs) were recorded at the OX. The effect of an intravitreal injection of tetrodotoxin (TTX) on the RCs elicited by electrical stimulation was also determined.
  
  
  RESULTS
  After electrical stimulation, RCs were observed at the optic disc, retinal arteries, and retinal veins. The two-dimensional maps of the RCs elicited by both TES and OX stimulation were similar. The latency of the RCs ranged from 2.0 to 4.0 s, and the peak occurred 6 to 9 s after the onset of the ES. The intensity of the RCs was correlated with the amplitude of EEP elicited by TES stimulation. The RCs disappeared after the TTX injection in both TES and OX stimulation.
  
  
  CONCLUSIONS
  TES activates principally the retinal ganglion cells, and a change in the blood flow is initiated thereafter.
authors.affiliation: Topcon Research Institute, Itabashi, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Mihashi
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Okawa
authors.forename: Tomomitsu
authors.initials: T
authors.lastname: Miyoshi
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Kitaguchi
authors.forename: Yoko
authors.initials: Y
authors.lastname: Hirohara
authors.forename: Takashi
authors.initials: T
authors.lastname: Fujikado
mesh_terms: D000818:Animals; D002415:Cats; D003315:Cornea; D003623:Dark Adaptation; D004558:Electric Stimulation; D005071:Evoked Potentials; D058449:Intravitreal Injections; D009897:Optic Chiasm / Q000502:physiology*; D010775:Photic Stimulation; D012160:Retina / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000502:physiology*; D013779:Tetrodotoxin / Q000008:administration & dosage
chemical_list: D013779:Tetrodotoxin