St Paul’s Eye Unit – Ophthalmology Royal Only
What is oral fluorescein angiography (FA)?
Angiography is a way of taking a picture of the blood vessels, and fluorescein is a dye that makes the blood vessels more visible. Fluorescein angiography (FA) is a diagnostic photographic test to give doctors more information about the condition affecting the back of your eye (the retina) to help decide on the most appropriate treatment for you.
Oral FA is a test in which several photographs are taken of the back of the eye after you drink juice or sweetened water mixed with a small amount of orange-yellow medical dye.
Why do we use dye?
The dye we use is fluorescein. The dye helps to give us a detailed view of the blood vessels in your retina. After fluorescein is swallowed, it moves around through the bloodstream and reaches the blood vessels that supply the retina. Shining a blue light on the retina makes these vessels fluoresce, making them easier to observe and photograph. This helps reveal blood flow in the retina and identify any abnormal or damaged vessels.
Why do I need the oral test?
FA is usually performed by injecting fluorescein dye into a vein of the arm, however, when this cannot be done, the dye can be administered by mouth in the form of a drink. This oral method is called ‘off‑label’ use of fluorescein.
What does it mean if a medicine is off-label?
In the UK, all medicines have a product licence (also called a marketing authorisation) from the MHRA which sets out how the medicine should normally be used and the way it should be given.
Sometimes, a medicine is used in a way that is not specifically licensed (for example, having it by mouth instead of the licensed injection method). This is called off‑label use, which is considered safe and effective. Oral fluorescein is a commonly used alternative when an injection is not suitable
What happens before the procedure?
Before the procedure, you will be weighed to ensure the correct dose of dye is mixed with either sweetened water or juice.
You will be asked to drink a small amount of water or juice with the dye dissolved in it. It is best to drink it quickly, then a set of images will be taken with the camera.
The time it takes for the dye to start to show at the back of the eye can vary from 5 to 25 minutes and the technician will take photographs at intervals every few minutes until the end of the test. The length of test varies from person to person depending on what is needed to be seen but usually takes around 30 minutes and no longer than 45 minutes to an hour.
How long does the procedure take?
The whole procedure will take approximately one hour.
However, you will have to stay in the clinic for 30 minutes after the test to ensure you have not suffered any side effects.
What should I expect from drinking the dye solution?
Fluorescein dye might give the skin or teeth a yellow tinge and your urine may be bright yellow for up to 48 hours after the test. Both are to be expected and are temporary and harmless. Drink plenty of water to flush the dye through the system
Most patients do not feel any side effects from the test apart from blurring of vision caused by the drops and some dazzle from the camera flash.
Are there side effects?
Oral FA has fewer side effects than when the dye is injected into a vein. Rarely, some patients may experience a feeling of nausea, this usually settles within minutes.
The skin may become itchy, and a rash may occur. If this happens, a doctor may need to prescribe an antihistamine.
In extremely rare cases, patients may experience a more severe reaction (anaphylaxis) during or after the test that might affect your breathing and heart rate. If this was to occur, we can deal with this emergency.
Can I have the test if I have eaten before coming to clinic?
Yes, you may eat and drink as normal prior to the procedure, although the dye will be absorbed faster if you haven’t eaten for two hours prior to the test.
Would it be okay to have the test if I am on tablets?
Yes, take any tablets or medications as normal before coming to the clinic, and please remember to bring a full list of current medication together with any over the counter or herbal products or privately-bought medications with you, also bring any inhalers you may be using.
When will I know the results?
In most cases you will see the doctor in clinic immediately following the test, who will go through the results with you.
In a small number of cases, you will need to come back to clinic for the results.
Feedback
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Further information
St Paul’s Outpatients Tel: 0151 706 3928
Text phone number: 18001 0151 706 3928
Author: St Pauls’ Eye Unit Dept
Review date: April 2029
PI 3242 V1