title: Digital image analysis of choroidal hypoperfusion in indocyanine green angiography using a choroid to disc gray-scale ratio.
abstract: OBJECTIVE
  To investigate hypoperfusion of the choroidal circulation in the macula, the brightness of the diffuse fluorescence of indocyanine green (ICG) angiogram (IA) was measured and the ratio of brightness of the macula to that of the disc was used for comparison of choroidal perfusion between different angiograms.
  
  
  METHODS
  Ten eyes of 10 young volunteers under 30 years of age (17-28 years old, average 24.7 years old), 10 eyes of 10 old volunteers over 60 years old (60-78 years old, average 66.7 years old) and 5 eyes of 5 patients with age-related macular degeneration (AMD) were examined by IA. The angiograms at 4 and 16 seconds after dye filling were used to measure the brightness of diffuse fluorescence at the macula and the disc on ICG angiograms with a 256-grade gray scale using the Topcon IMAGEnet computer system. The ratio (ch/d ratio) of the averaged brightness of the macula to that of the disc was calculated for each angiogram.
  
  
  RESULTS
  The ch/d ratios of the angiograms 4 seconds after dye filling were 1.41 in the young volunteers, 1.23 in the old volunteers and 0.52 in the AMD patients. The ch/d ratios of the angiograms 16 seconds after dye filling were 0.92 in the young volunteers, 1.02 in the old volunteers and 0.80 in AMD. There were significant differences in the ch/d ratios among the 3 groups 4 seconds after dye filling (p=0.007, Kruskal-Wallis H test,) but there were no significant differences 16 seconds after dye filling (p=0.310).
  
  
  CONCLUSIONS
  The ch/d ratio is an adjunctive method for detecting choroidal hypoperfusion in IA, and may be helpful for objective evaluation of the choroidal circulation in chorioretinal diseases.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Osaka City University, Graduate School of Medicine, Japan. noritomiki@hotmail.com
authors.forename: Norito
authors.initials: N
authors.lastname: Miki
authors.forename: Takeya
authors.initials: T
authors.lastname: Kohno
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Shiraki
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Nadachi
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Okazaki
authors.forename: Jun
authors.initials: J
authors.lastname: Suehiro
authors.forename: Yoko
authors.initials: Y
authors.lastname: Uenishi
authors.forename: Tokuhiko
authors.initials: T
authors.lastname: Miki
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D016022:Case-Control Studies; D002829:Choroid / Q000098:blood supply* / Q000473:pathology / Q000503:physiopathology; D004396:Coloring Agents; D003720:Densitometry; D005451:Fluorescein Angiography / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007208:Indocyanine Green; D008266:Macula Lutea / Q000098:blood supply* / Q000473:pathology / Q000503:physiopathology; D008268:Macular Degeneration / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D008875:Middle Aged; D010477:Perfusion / Q000379:methods; D012039:Regional Blood Flow / Q000502:physiology; D012984:Software
chemical_list: D004396:Coloring Agents; D007208:Indocyanine Green