Digital Indocyanine Green (ICG) Angiography

Indocyanine Green (ICG) angiography focuses on an important layer of blood vessels just beneath the retina called the choroid. These blood vessels serve several important roles in the eye, including supplying the retina with oxygen and nutrients. The choroidal vessels cannot be directly visualized by retinal examination or fluorescein angiography, but they can be imaged using ICG angiography.

In a manner similar to fluorescein angiography, ICG dye is injected into a vein in the arm. A digital camera is used with certain light filters, to highlight the choroidal blood vessel layer located underneath the retinal layers. ICG angiography can be performed as a stand-alone test. However, it is often used in conjunction with fluorescein angiography to provide a more complete picture of the blood vessels in the back of the eye.

ICG imaging of the choroidal vessels is useful when evaluating certain types of retinal diseases. Age-related macular degeneration and inflammatory diseases of the retina are two diseases where ICG can be particularly helpful. For example, ICG angiography can be used as a supplement to fluorescein angiography to diagnose the "wet" form of macular degeneration that may be undetectable with fluorescein angiography alone.