ICG angiography of the eye

Indocyanine Green (ICG) angiography is an imaging test that visualizes blood vessels within the eye, primarily focusing on the choroid, a vascular layer located beneath the retina. The choroid is rich in blood vessels and supplies oxygen and nutrients to the outer retina. Unlike fluorescein angiography (FA), which mainly images retinal vessels, ICG angiography allows for the visualization of deeper choroidal vessels, even when obscured by hemorrhage or fluid.

ICG angiography is used to diagnose and monitor various eye conditions affecting the choroid and its blood supply. It is particularly effective in identifying choroidal vascular pathologies such as wet age related macular degeneration (AMD), central serous retinopathy, and inflammatory conditions of the choroid (choroiditis). This test complements the information obtained from FA, providing a more comprehensive understanding of the eye's vascular status.

The test is performed while seated. Typically, eye drops are administered to dilate the pupils. Following dilation, indocyanine green (ICG) dye is injected into a vein in the arm. The dye rapidly circulates through the bloodstream and reaches the eye's blood vessels. A specialized camera equipped with appropriate filters then captures a series of images of the fundus over time, documenting the dye's passage through the vessels. These images highlight areas of normal blood flow, abnormal vessels, leakage, or blockages.

It is crucial to inform the medical team about any known allergies, especially to contrast agents, as well as any medical conditions such as asthma, liver disease, pregnancy, or breastfeeding. A previous hypersensitivity reaction to ICG is a contraindication to receiving it again. Report any previous reaction to injected dyes, contrast agents or iodide containing products, and describe what happened. Some ICG preparations contain sodium iodide and carry product specific precautions. Seafood allergy alone is not the same as allergy to ICG. The medical team must assess suitability using the actual product and your reaction history. In some cases, an assessment of liver function may be required. Fasting is generally not necessary before the test, but specific instructions should be discussed with the treating team. Patients should arrange for a companion and bring sunglasses, as pupil dilation will cause blurred vision and light sensitivity.

Most side effects of ICG are mild and temporary, including mild nausea, vomiting, dizziness, rash, or itching. In very rare instances, more severe allergic reactions can occur, such as shortness of breath, pulmonary edema, or anaphylaxis. It is important to immediately report any unusual sensations to the medical staff during or after the test. The contrast agent is primarily cleared from the body by the liver.

After the test, vision may be blurred and light sensitive for several hours due to pupil dilation. Therefore, driving is not permitted, and activities requiring sharp vision should be avoided. For breastfeeding mothers, specific instructions should be discussed with the treating team. The captured images are interpreted by a specialized ophthalmologist, and the results aid in diagnosis and in tailoring a treatment plan.

In most cases, recovery after the test is quick and uneventful. However, if symptoms such as shortness of breath, chest pain, widespread rash, facial or throat swelling, or any other severe allergic reaction occur, immediate medical attention should be sought. Although rare, these symptoms require prompt evaluation and treatment.