Indocyanine Green Angiography, or ICGA, is a highly specialized diagnostic imaging test used to examine the blood circulation in the choroid, the layer of blood vessels situated beneath the retina. This advanced procedure provides your retina specialist with critical information that is often not visible with other imaging techniques. At Pristine Eye Hospitals, we use ICGA to achieve a precise diagnosis for complex retinal and uveal disorders.
What is a ICGA (Indocyanine Green Angiography)?
ICGA is a diagnostic procedure that involves injecting a water-soluble, green-colored dye called indocyanine green (ICG) into a vein in your arm. As the dye travels through your bloodstream to the eye, a specialized digital camera using infrared light takes rapid-sequence photographs of the back of your eye. Because ICG dye glows under this invisible light, it allows our specialists to clearly visualize the blood vessels of the choroid, which are otherwise obscured by the retinal pigment epithelium (RPE) layer.
Why is this test performed?
Your retina specialist may recommend an ICGA to diagnose, evaluate, or manage several conditions affecting the choroid and retina. Key indications include:
Wet Age-Related Macular Degeneration (AMD): To identify abnormal blood vessel growth beneath the retina, especially when bleeding obscures the view in other tests.
Polypoidal Choroidal Vasculopathy (PCV): ICGA is the gold standard for diagnosing this condition, which involves abnormal, polyp-like dilations in the choroidal blood vessels.
Choroidal Tumors & Inflammation: To assess blood flow patterns in intraocular tumors and to evaluate inflammatory conditions like posterior uveitis or choroiditis.
Central Serous Chorioretinopathy (CSCR): To identify specific areas of leakage from the choroid that cause fluid to accumulate under the retina.
How to Prepare for Your ICGA (Indocyanine Green Angiography)
Preparation for an ICGA is minimal. It’s important to inform your doctor about any known allergies, particularly to iodine or shellfish, as the ICG dye contains iodine. Since your pupils will be dilated for the test, you should arrange for someone to drive you home afterward.
Your pupils will be dilated with eye drops, causing temporary light sensitivity and blurred vision for several hours.
Remember to bring a pair of sunglasses for your comfort on the way home.
You may be asked to fast for a few hours before the procedure, but your doctor will provide specific instructions.
The Procedure: What to Expect Step-by-Step
1. First, dilating drops will be administered to widen your pupils, allowing for a clear view of your retina. You will then be seated comfortably in front of the specialized ICGA camera.
2. A small amount of indocyanine green dye is injected into a vein in your arm. The injection is quick and feels similar to a standard blood test.
3. As the dye circulates to your eyes, the camera will take a rapid series of infrared photographs over a period of about 15-20 minutes. You will be asked to look in different directions, but the process is entirely painless.
4. Once the images are captured, the procedure is complete. Your specialist will review the images, and you can leave after a brief observation period, keeping in mind that your vision will remain blurry until the dilating drops wear off.
Understanding Your Results
The images produced by the ICGA provide a detailed “map” of the blood flow within the choroidal layer of your eye. Your retina specialist at Pristine Eye Hospitals will carefully analyze these images to identify any abnormalities, such as leaking blood vessels, blockages, inflammation, or abnormal vessel networks characteristic of conditions like PCV or wet AMD.
This precise information is vital for confirming a diagnosis that might otherwise be uncertain. Based on the ICGA findings, your doctor can formulate the most effective and targeted treatment plan for your specific condition, which they will discuss with you in detail during your follow-up consultation.
Frequently Asked Questions
Is the ICGA test painful?
The test itself is not painful. You may feel a slight, brief prick in your arm when the dye is injected, but there is no discomfort during the imaging process itself.
Are there any side effects from the ICG dye?
Side effects are very rare. Some patients may experience mild, temporary nausea, but significant allergic reactions are extremely uncommon.
How is ICGA different from a Fluorescein Angiography (FFA)?
While both tests image blood vessels, ICGA uses a different dye and infrared light to see deeper structures within the choroid. An FFA uses a yellow dye (fluorescein) and is better for visualizing the blood vessels of the retina itself.