Indocyanine Green Angiography
Fluorescein angiography has proven helpful in demonstrating and directing laser treatments to well defined “classic” neovascular lesions secondary to age-related macular degeneration (ARMD). However, studies have shown that between 50 and 85% of exudative “wet” ARMD lesions are of the “occult” variety, not amenable to laser treatment.
Although Indocyanine Green (ICG) dye was in existence over a quarter century ago, it was not until high sensitivity solid state cameras became available that ICG imaging became a reality for the retina specialist. By imaging in the near-infrared spectrum we are now able to observe retinal pathology (disease) previously obscured by blood, lipid, and normal ocular pigment. Furthermore, by virtue of being highly protein bound, the ICG dye does not leak excessively from the choroidal vasculature as does standard fluorescein dye, allowing excellent demonstration of the vascular choroid, which lies between the retina and the sclera.
ICG technology, now available in our offices, has proven most useful in the detection and laser ablation of so called “hot spots”, indicating areas of active neovascularization in ARMD. With standard fluorescein angiography the standard protocol had been to treat everything with laser, including areas of the retina that might be uninvolved, because it was difficult to differentiate between the two. The ICG technology now allows us to look at a deeper section of the eye and see what is happening beneath the blood, so we can spare those unaffected areas.
ICG also gives insight into diseases that involve the layer deeper to the retina called the choroid. This is especially helpful for central serous retinopathy and certain inflammatory diseases known as uveitis.