What Is Indocyanine Green Angiography (ICG)?

How Does ICG Imaging Differ from Standard Fluorescein Angiography?

While both tests use dye to map blood vessels, they focus on different layers of the eye. Fluorescein Angiography is best for seeing the retinal vessels, but the dye often leaks and clouds the view of the deeper layers. ICG dye stays inside the larger vessels of the choroid and does not leak as easily, providing a much cleaner picture of the deep ocular circulation. By using infrared light, ICG can penetrate through hemorrhages and fatty deposits that frequently obscure the vision of standard cameras during a clinical evaluation.

What are the Primary Diagnostic Data Trends for Choroidal Disease?

Clinical data suggests that ICG angiography increases the diagnostic accuracy for certain macular conditions by nearly 30 percent. In patients with wet macular degeneration who do not respond to standard injections, an ICG scan often reveals hidden polyps or vessels that were missed on other scans. These polyps require a different treatment approach, such as specialized laser therapy. The ability to identify these hidden vascular structures is why ICG is considered an essential tool in advanced retinal specialty clinics.

Why is Dye Sensitivity and Allergy Screening Mandatory for ICG?

The ICG dye contains a small amount of iodine, which can trigger an allergic reaction in sensitive individuals. Before the test, clinicians must carefully screen patients for any history of iodine or shellfish allergies to ensure their safety. While severe reactions are rare, occurring in less than 1 percent of cases, the office must be equipped with emergency medications to treat any hives or breathing issues. Ensuring a safe injection environment is a mandatory part of the clinical protocol for any vascular imaging procedure.

What are the Most Common Referral Clues for an ICG Scan?

Retinal specialists typically order an ICG scan when a patient has unexplained fluid or bleeding in the back of the eye. Classic referral clues include cases of Central Serous Chorioretinopathy that do not resolve or suspicions of intraocular tumors that need to be mapped. It is also used extensively in the diagnosis of uveitis, where it can show areas of the choroid that are inflamed even when the retina appears healthy. Identifying these deep inflammatory markers allows for more precise and effective medical management.

How Do Clinicians Use ICG to Plan Specialized Laser Treatments?

Because ICG provides a clear map of the abnormal vessels, it is often used as a surgical guide for laser therapy. The doctor can use the ICG images to target the exact source of the leak while avoiding the healthy parts of the macula. This precision is necessary for procedures like Photodynamic Therapy, where a specific wavelength of light is used to close down leaky vessels. The integration of ICG imaging with laser technology has significantly improved the visual outcomes for patients with difficult-to-treat choroidal diseases.