Indocyanine green angiography

LDHvsICG (cropped)

Indocyanine Green Angiography (ICGA) is a medical imaging technique used in ophthalmology and cardiology to visualize blood flow in the choroid, retina, and heart. This procedure involves the intravenous injection of Indocyanine Green (ICG), a fluorescent dye that binds tightly to plasma proteins and allows for imaging of the blood vessels.

Overview

ICGA is particularly useful for diagnosing and managing conditions affecting the choroidal and retinal circulation. In ophthalmology, it provides critical information for the diagnosis and treatment of conditions such as Age-related Macular Degeneration (AMD), Central Serous Chorioretinopathy (CSC), and Choroidal Tumors. The technique is advantageous over traditional fluorescein angiography because ICG's infrared fluorescence is not obscured by hemorrhages or pigment in the retina, allowing for better visualization of the choroidal circulation.

Procedure

The ICGA procedure involves the intravenous injection of Indocyanine Green dye. Once injected, the dye travels through the bloodstream to the eye's choroidal and retinal vessels. A camera equipped with special filters captures the fluorescence emitted by the dye as it circulates through the blood vessels, creating detailed images of the vascular structure. The procedure is typically performed in an outpatient setting and takes about 10-30 minutes.

Applications

ICGA is used in the diagnosis and management of various ophthalmic conditions:

• Age-related Macular Degeneration (AMD): ICGA helps in identifying choroidal neovascularization not visible on fluorescein angiography.
• Central Serous Chorioretinopathy (CSC): The technique can visualize abnormal choroidal vessels associated with CSC.
• Choroidal Tumors: ICGA assists in differentiating between benign and malignant choroidal tumors.
• Polypoidal Choroidal Vasculopathy (PCV): ICGA is crucial for diagnosing PCV, a variant of neovascular AMD.

Advantages and Limitations

The primary advantage of ICGA over fluorescein angiography is its ability to image the choroidal circulation, which is not possible with fluorescein angiography due to its absorption and blockage by retinal pigment epithelium. However, ICGA is more expensive and not as widely available as fluorescein angiography. Additionally, the interpretation of ICGA images requires specialized training and expertise.

Safety

ICG is generally well tolerated, with a low incidence of adverse reactions. The most common side effects are mild and transient, including nausea and vomiting. Severe allergic reactions are rare. Patients with iodine allergy, shellfish allergy, or those with severe liver disease should avoid ICGA.

Conclusion

Indocyanine Green Angiography is a valuable diagnostic tool in ophthalmology, providing detailed images of the choroidal and retinal circulation. Its ability to visualize blood flow in areas not accessible by other imaging modalities makes it indispensable for the diagnosis and management of various eye diseases. Despite its advantages, the technique's availability and the need for specialized interpretation limit its use to specialized centers.