are there. The concentration of indocyanine green dye may vary according to instrument used. For fundus cameras, 25 ml ICG dissolved in 5 ml solvent is used, it may be increased to 50 ml in patients with poorly dilated pupil and high pigmentation. In case of iodine allergy, instead of ICG, iodine-free dye Infracyanine green should be used. To perform test, pupil should be dilated. The dye is injected through the antecubital vein as bolus. Images are taken in several second intervals until the retinal and choroidal circulations are maximally hyperfluorescent. Then for first few minutes, take photos at approximately 30 to 60 second intervals. Pictures taken are classified under three phases: Early phase at 60 seconds: large choroidal arteries and veins are highlighted in this phase. Mid phase at 5-15 minutes: in this phase choroidal vasculature become less distinct and more diffuse, and hyperfluorescent lesions appear bright against the fading background. Late phase at 15-30 minutes: in this phase hyperfluorescent lesions appear bright against the dark background. The choroidal neovascularization are best detected in this phase. Advantages over fluorescein angiography Indocyanine green angiography has many advantages over commonly used fundus fluorescein angiography (FFA). Because of its protein-bounding properties, its leakage from choriocapillaries is less and thus it will remain longer in choroidal vessels compared to fluorescein dye. Choroidal neovascularization is better visualized by ICGA, than fluorescein angiography. The patient toleration is also better compared to FFA. History Physical and physiological properties of indocyanine green dye were first described by Fox and Wood, in 1960. Indocyanine green angiography was developed by Kodak Research Laboratories for determining cardiac output. In 1968, Kogure et al. performed intra-arterial choroidal absorption angiography using indocyanine green dye in monkeys. In the year 1969, using ICGA, Kogure and Choromokos studied cerebral circulation in a dog. In 1971, Hochhimer replaced color film with black and white infrared film. First human ICG angiogram was of carotid artery. First intravenous ICGA in human eye was performed by Flower and Hochheimer in 1972. In 1986 Hayashi et al. used infrared-sensitive video camera to perform ICGA. In the year 1992, Guyer et al. introduced the use of high resolution (1024 × 1024) digital imaging system coupled with infrared video cameras to produce better high resolution images. See also Fundus photography Fundus fluorescein angiography Eye examination Reference Eye procedures Optical imaging Diagnostic ophthalmology