ABSTRACT
Indocyanine green angiography (ICGA) is a form of angiography performed less commonly than fluorescein angiography. Indocyanine green (ICG) angiograms are considered to be a choroidal angiogram, as the ICG dye is bound to plasma proteins in the blood and dose not diffuse into tissue, as seen with fluorescein dye. Most ICG angiograms are performed on mydriatic fundus camera systems, though more are being performed on confocal scanning laser ophthalmoscope (cSLO) systems using video capture. Fundus cameras used to perform ICG are fundamentally different from standard fundus cameras in that they must be capable of imaging in the infrared portion of the electromagnetic spectrum, requiring modifications to the optics, filtration and sensor systems. Digital imaging technology changed everything, given the digital sensor's inherent sensitivity to infrared. In fact, CCD sensors are so sensitive to infrared that most commercial sensors are manufactured with a filter to block infrared radiation, called a hot mirror.
