What is Angiography?
Angiography is a minimally invasive imaging technique that is used to highlight the location of blood vessels in various organs in the body. It usually involves injecting a contrast substance into the bloodstream and then using an imaging technique to visualize the contrast flowing through blood vessels.
Angiography for macular degeneration
This can be especially important when studying diseases of the eye, including macular degeneration, particularly wet AMD or CNV in myopic macular degeneration. Wet AMD and CNV in myopic MD involve the growth of abnormal blood vessels under the retina and possible leakage of those vessels. Being able to properly visualize them is important for monitoring disease activity and evaluating treatment effectiveness.
Types of angiography
Two types of angiography, named fluorescein angiography (FA) and indocyanine green angiography (ICG), are typically employed in macular degeneration. Your doctor might use one or both of these techniques to assist them in diagnosis and treatment decisions for your macular degeneration.
Fluorescein angiography (FA)
First used in the eye in 1961, fluorescein angiography (FA) has become one of the most fundamental imaging tests used in ophthalmology.1 It helps your eye doctor visualize blood vessel patterns to differentiate between various retinal conditions and also allows him/her to see whether laser treatment might be beneficial.
Fluorescein angiography process
- During the procedure, a substance called sodium fluorescein is first injected into a vein in your arm.
- It then travels quickly through your bloodstream and into blood vessels of the eye, first filling the arterioles of the retina, followed by the capillaries and venules.
- The same camera used in fundus photography takes pictures of the eye as the dye travels through the blood vessels.
- Then, filters are used to single out the light from the fluorescent dye.
- After about 10 minutes or so, the dye will clear completely from the eye, and will eventually be cleared from your body by your kidneys.
If there is disease affecting of the blood vessels of the eye, then the dye may leak, stain, or be blocked in a way that will help alert your doctor to the abnormalities.
Fluorescein angiography side effects
Although generally considered safe, FA may have some side effects.
- You may notice mild nausea after receiving the dye.
- It is also typical to have orange appearing sweat or urine for 1-2 days following FA, and this should not alarm you.
- Rarely, one may develop an allergic reaction causing severe itching, rash, or difficulty breathing – if you notice these symptoms, you should alert your doctor immediately.
Indocyanine green angiogram (ICG)
Indocyanine green angiography (ICG) is similar to FA, but instead of using sodium fluorescein, it uses indocyanine green dye, which fluoresces under infra-red light.2 ICG is used to get images of the choroid, or the layer of blood vessels and tissue between the white of the eye (called the sclera) and the retina.2 An infra-red camera is used, and it’s able to get images of the blood circulation within layers of tissue in the choroid.
Differences between ICG and FA
Similar to FA, the dye is injected into a vein in your arm, and it travels to the choroidal and retinal circulation. However, ICG dye stays trapped in the choroidal blood vessels longer than fluorescein dye, which clears out of the choroid fairly quickly. For this reason, ICG is used primarily for imaging the circulation in the choroid, whereas FA is used more often for imaging the circulation of the retina. The two tests can be used to complement each other, and to give your doctor a more comprehensive picture of your eye.
Other diagnostic tests
There are many different imaging tests of the eye, and many are used together to thoroughly evaluate the status of your eye condition and how best to pursue treatment. Talk with your doctor about what different imaging techniques are available, and which ones might be best for your eye condition.