Effects of indocyanine green on retinal ganglion cells.
OBJECTIVE
Recently, indocyanine green (ICG) has been used to visualize the internal limiting membrane during vitrectomy. After intraocular administration, ICG accumulates at the optic disc. In this study, the effects of ICG on retinal ganglion cells (RGCs) were examined.


METHODS
In vitro, rat RGCs were purified by a two-step immunopanning procedure, briefly exposed to ICG (2.5 x 10(3) mg/L), and irradiated with an endoilluminator for 15 minutes or incubated in the presence of ICG (concentration: 2-250 mg/L) without irradiation. The number of viable RGCs was counted after 3 days in culture. In vivo, after rats received an intravitreal injection of 3 micro L ICG (0.25 and 2.5 mg/L), the distribution of ICG was observed with a fundus camera, and the number of viable RGCs was examined by a DiI (1,1'-dioctadecyl-1-3,3,3',3'-tetramethylindocarbocyanine perchlorate)-retrolabeling technique.


RESULTS
In vitro, a brief exposure to ICG and light did not affect RGC survival. However, ICG reduced the number of viable RGCs in a dose-dependent manner when the cells were exposed for 3 days. In vivo, the dye was initially distributed on the retinal surface and around the optic disc. At day 7, the fluorescence became invisible in the 0.25-mg/L group, whereas the staining of the optic disc contour was evident in the 2.5-mg/L group. The number of viable RGCs decreased significantly in the 2.5-mg/L group 14 days after the injection.


CONCLUSIONS
ICG showed an inherent toxicity to RGCs in a dose-dependent manner. Lower concentration and shorter staining time of ICG should be used for dye-assisted vitrectomy.
Department of Ophthalmology, University of Tokyo School of Medicine, Tokyo, Japan.
Aya
A
Iriyama
Saiko
S
Uchida
Yasuo
Y
Yanagi
Yasuhiro
Y
Tamaki
Yuji
Y
Inoue
Kyosuke
K
Matsuura
Kazuaki
K
Kadonosono
Makoto
M
Araie
D000818:Animals; D002452:Cell Count; D002470:Cell Survival; D002478:Cells, Cultured; D004396:Coloring Agents / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D007208:Indocyanine Green / Q000633:toxicity*; D007267:Injections; D051381:Rats; D017208:Rats, Wistar; D012165:Retinal Ganglion Cells / Q000187:drug effects* / Q000473:pathology / Q000528:radiation effects; D014822:Vitreous Body
D004396:Coloring Agents; D007208:Indocyanine Green