title: Histologic localization of indocyanine green dye in aging primate and human ocular tissues with clinical angiographic correlation.
abstract: OBJECTIVE
  This study aimed to histologically localize indocyanine green (ICG) dye in the geriatric primate and human eye and to correlate these findings with clinical ICG angiography.
  
  
  METHODS
  The study design was a clinicopathologic correlation.
  
  
  METHODS
  Six eyes of three geriatric monkeys (Maccaca mulatta) with macular drusen, 19 to 29 years of age, housed at the California Primate Research Center and an enucleated human eye from a 66-year-old patient with choroidal melanoma were examined.
  
  
  METHODS
  All six monkey eyes and the human eye underwent clinical ICG angiography. Five monkey eyes were enucleated at varying intervals after intravenous ICG dye injection for histologic examination. One monkey eye was removed without prior ICG injection as an age-matched control. The human eye was enucleated after intravenous injection of ICG dye.
  
  
  METHODS
  Infrared fluorescence microscopy of freeze-dried tissue sections was performed to detect ICG fluorescence. Histologic sections were stimulated with an 810-nm diode laser, and the fluorescence emitted was detected with a Hamamatsu infrared camera. The images were digitally recorded. The distribution of fluorescence on histologic examination was correlated with the fluorescence of the clinical ICG angiogram.
  
  
  RESULTS
  Infrared fluorescence microscopy of monkey sections localized fluorescence within retinal and choroidal vessels early after injection of ICG dye. The ICG fluorescence was seen in the extravascular choroidal stroma within 10 minutes after injection. The stromal fluorescence persisted in sections obtained 50 minutes after injection of ICG. The retinal pigment epithelium (RPE)-Bruch's membrane complex was brightly fluorescent in the middle- and late-stage histologic sections. Drusen deposits were brightly fluorescent at all timepoints examined. Similar findings were observed in freeze-dried tissue sections of the human eye. The fluorescence detected on histologic sections correlated closely with the fluorescence of the clinical ICG angiograms for the same interval.
  
  
  CONCLUSIONS
  The ICG dye does not remain solely within the choroidal intravascular space but extravasates into the choroidal stroma and accumulates within the RPE. Extravascular ICG binds to drusen material. These findings will enhance the interpretation of clinical ICG angiography.
authors.affiliation: Department of Ophthalmology, University of California, Davis, Sacramento, California 95816, USA.
authors.forename: A A
authors.initials: AA
authors.lastname: Chang
authors.forename: L S
authors.initials: LS
authors.lastname: Morse
authors.forename: J T
authors.initials: JT
authors.lastname: Handa
authors.forename: R B
authors.initials: RB
authors.lastname: Morales
authors.forename: R
authors.initials: R
authors.lastname: Tucker
authors.forename: L
authors.initials: L
authors.lastname: Hjelmeland
authors.forename: L A
authors.initials: LA
authors.lastname: Yannuzzi
mesh_terms: D000368:Aged; D000375:Aging / Q000378:metabolism*; D000818:Animals; D002829:Choroid / Q000378:metabolism* / Q000473:pathology; D002830:Choroid Neoplasms / Q000378:metabolism / Q000473:pathology; D005260:Female; D005451:Fluorescein Angiography; D005456:Fluorescent Dyes / Q000493:pharmacokinetics*; D005612:Freeze Drying; D006801:Humans; D007208:Indocyanine Green / Q000493:pharmacokinetics*; D008253:Macaca mulatta / Q000378:metabolism*; D008545:Melanoma / Q000378:metabolism / Q000473:pathology; D008856:Microscopy, Fluorescence; D008992:Monkey Diseases / Q000378:metabolism / Q000473:pathology; D012160:Retina / Q000378:metabolism* / Q000473:pathology; D015593:Retinal Drusen / Q000378:metabolism / Q000473:pathology / Q000662:veterinary; D014018:Tissue Distribution
chemical_list: D005456:Fluorescent Dyes; D007208:Indocyanine Green