title: Nonaxoplasmic transfer of indocyanine green into the optic nerve after intravitreal application.
abstract: OBJECTIVE
  To investigate whether indocyanine green (ICG) migrates into the optic nerve after intravitreal application in the rabbit eye.
  
  
  METHODS
  Gas vitrectomy was performed in one eye of adult Dutch belted rabbits by pars plana injection of 0.4 ml of 100% C3F8 (n = 10). One week later, vitrectomy was performed and 0.2 ml of 0.25% ICG was instilled into the vitreous cavity of these vitrectomized eyes. After 30 seconds of ICG application, the vitreous cavity was rinsed with balanced salt solution plus. Unoperated rabbits served as controls (n = 2). Globes, optic nerves, and the entire brain were removed, and ICG fluorescence of the specimens was examined with a digital fundus camera starting from the first day to the fourth postoperative week. Other rabbit eyes (n = 2) were injected with ICG directly into the vitreous without vitrectomy, and assessed for ICG signal after 1 day of ICG application. In the second part of the experiment, four rabbit eyes were gas vitrectomized and ICG was instilled onto retina after blockage of axonal flow by vinblastine. They were evaluated on the first (n = 2) and seventh postoperative days (n = 2).
  
  
  RESULTS
  No fluorescein was detected in the visual pathways and the brains of the control group of rabbits. The optic nerves of the ICG-instilled eyes were stained diffusely with ICG starting from the first day after surgery. ICG injected nonvitrectomized eyes showed similar ICG staining patterns when compared with vitrectomized eyes. ICG staining pattern of the optic nerve did not differ in vinblastine-pretreated eyes. Fluorescence extended along the intraorbital portion of the optic nerve but did not transport more posteriorly in all animals. At the fourth week after vitrectomy, ICG signal was still detectable, but staining was less intense.
  
  
  CONCLUSIONS
  Intravitreal ICG injection results in nonaxoplasmic extension into the optic nerve in the rabbit.
authors.affiliation: Department of Ophthalmology, Osaka University Medical School, Japan.
authors.forename: Osman
authors.initials: O
authors.lastname: Cekiç
authors.forename: Takeshi
authors.initials: T
authors.lastname: Morimoto
authors.forename: Masahito
authors.initials: M
authors.lastname: Ohji
authors.forename: Miki
authors.initials: M
authors.lastname: Sawa
authors.forename: Takuya
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Sakaguchi
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ikuno
authors.forename: Fumi
authors.initials: F
authors.lastname: Gomi
authors.forename: Motohiro
authors.initials: M
authors.lastname: Kamei
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Tano
mesh_terms: D000818:Animals; D001370:Axonal Transport / Q000187:drug effects; D001692:Biological Transport; D004396:Coloring Agents / Q000493:pharmacokinetics*; D015590:Fluorophotometry; D007208:Indocyanine Green / Q000493:pharmacokinetics*; D007267:Injections; D009900:Optic Nerve / Q000378:metabolism*; D011817:Rabbits; D014747:Vinblastine / Q000494:pharmacology; D014821:Vitrectomy; D014822:Vitreous Body / Q000378:metabolism*
chemical_list: D004396:Coloring Agents; D014747:Vinblastine; D007208:Indocyanine Green