Originally published by Harvard Health.
What is the test?
By looking into the back of your eye (the retina), eye doctors can see if there are changes in the blood vessels. Certain changes increase your risk of vision loss from diabetes or other conditions. The earliest changes can be seen only with a special test called fluorescein angiography.
For this test, a chemical is injected into a vein in your hand or arm while the eye doctor is looking at the back of your eyes with a special instrument. The chemical called fluorescein temporarily lights up the blood vessels. The eye doctor can easily see if there are leaks or other abnormal changes in the vessels.
How do I prepare for the test?
You should arrange to have someone else drive you home from the eye doctor because your eyes will be dilated. This can make your eyes sensitive to the sun and your vision blurry for a while.
What happens when the test is performed?
You have drops put into your eye to make the pupil dilate (open). You have to wait for about 30 minutes while the drops take effect. Before giving you any other medicine, your doctor will first examine your eyes.
A medical professional inserts a small needle into a vein. Fluorescein dye is injected in the vein. Your doctor uses a special eye camera to take pictures of your retina. You look into one side of the camera while your doctor looks through the other side. The camera shines a dim blue light into your eye, which causes the dye flowing through the retina arteries to show up as fluorescent green. The doctor takes a collection of pictures of your eyes to review more closely later.
What risks are there from the test?
There are no special risks from this test. Your vision may be blurry for an hour or more after the test because your pupils are dilated. The dye fluorescein is excreted from your body in your urine. This might give your urine a bright or discolored appearance for a day.
Must I do anything special after the test is over?
You will need to wear sunglasses for a few hours until your pupils are no longer dilated.
How long is it before the result of the test is known?
Your doctor can often discuss the results of the test with you at the end of your visit. He or she might recommend treatment (such as eye laser treatments) if your test reveals retina disease.