Indocyanine green angiography or ICGA is a diagnostic test used to evaluate the circulation of the retina; the neurosensory tissue of the eye that transmits the optical images we see into the electrical images our brain understands, as well as deeper into the choroid; the layer behind the retina that provides oxygen and nourishment to the outer layer of the retina. The main advantage of the ICGA test is that it allows specific analysis of the choroidal vessels and their interaction with the retina.
What can I expect during an ICGA test?
After your eyes are dilated, the physician or nurse will use a butterfly needle to inject a small amount, (5ml) of Indocyanine green dye into the vein of your arm or hand. The butterfly needle is then removed. The dye only takes moments to reach the eye so you will be positioned in the camera at the time of injection when a live high-resolution video will be obtained. Special filters are used in the camera that allow the dye to fluoresce and even subtle changes can be noted in choroidal blood flow. The actual test itself takes about 20-30 minutes once the injection is complete while a specific series of timed videos and photographs are taken. This test is usually ordered in combination with other imaging techniques in order to best evaluate your retina.
Are there side effects to an ICGA test?
The test is considered to be safe for most patients. Rare, allergic reactions to indocyanine green can occur, effecting less than 0.2% of patients in which itching with rash and/or hives, and nausea may be experienced. If you were to have this reaction, it would occur moments after the test began while under the physician’s care. In most cases, these symptoms can be managed with an oral antihistamine tablet, such as Benadryl and the allergic reaction will cease within minutes. However, patients with an allergy to iodine or shellfish should inform the physician as ICG dye would be contraindicated in these cases.