What is a fluorescein angiography and ICG angiography?

These are simple diagnostic tests which involve a nurse placing a cannula (a small plastic tube that sits in the vein) into a vein in either the hand or arm. A small amount of fluorescein (yellow) dye and/or indocyanine green is administered into the bloodstream via the cannula, followed by a series of photographs of the back of the eye taken with a fundus camera over several minutes.

A fundus fluorescein angiogram test gives the doctor more information about the condition of your retina, the light-sensitive layer at the back of the eye. The ICG angiogram test provides information about the choroid – the layer of blood vessels – underneath the retina.

Looking at the photographs from your fundus fluorescein angiogram/ ICG angiogram will provide information about the condition of your eyes and will help the doctor make a diagnosis and plan any necessary treatment.

What happens when I arrive at my appointment?

When you come to the clinic you will have your vision tested, your eye pressure checked, and dilating eye drops instilled. If you are elderly or have a long way to come to the hospital, it is advisable to bring someone with you to the appointment.

As you will have dilating drops that may blur your vision for a few hours, we ask you to please not drive to this appointment. Please take any medications as normal and ensure you have had something to eat and drink before the procedure.

What happens during the procedure?

  • A photographer will take two scans and a series of photographs to begin with.
  • A cannula will be fitted in your hand or arm through which we will introduce a small amount of dye called fluorescein and/or indocyanine green.
  • As the dye is introduced, we will immediately begin taking photographs using a special camera to capture the circulation of the dye in your blood vessels at the back of your eye. It only takes around 20 seconds for the dye to reach the vessels in the back of your eye from the vessels in your hand or arm.
  • It is important that you try and stay as still as possible and keep your eyes open while we take the photographs, so we get a good clear view of the back of your eye.
  • The photographer will take photographs for 10 minutes in total for fluorescein angiography and 30 minutes for indocyanine green angiography – you will be able to blink and take a little break if necessary.
  • After the procedure, the nurse will remove the cannula from your arm, and you will either be seen by a doctor, or a follow-up appointment will be made.

The photographer and the nurse will guide you through the entire procedure and you are free to ask any questions at any point.

Are there any side-effects?

The fluorescein dye may give your skin a slight yellow colour and your urine will be very bright yellow for the next 24-48 hours. This is normal, it is just the dye leaving your body.

Drink plenty of fluids to help the dye leave your body. The indocyanine green dye will not have any effect on either your skin or urine.

Occasionally, when the dye enters your veins in the first one to two minutes of the procedure, you may feel nausea. This is generally a very brief sensation and should pass quickly. Very occasionally the nausea may lead to vomiting.

Very rarely the dye can cause an allergic reaction which may take the form of breathing difficulties or circulatory difficulties (anaphylaxis). We are equipped to deal with this emergency and if it happens the emergency medical team will be contacted.

If you have any allergies, asthma or if you have had a reaction to a dye test before, please inform us.

How long will I be at the hospital?

The procedure itself takes between 10 to 30 minutes. The dilating eye drops take 30 minutes to dilate your eyes fully and cannulation time can vary depending on how easy it is to access your veins (ensuring that you have drunk sufficient fluids will help with this). You may wish to rest a while before leaving the clinic, so you should allow two hours in total.

We attempt to keep appointment times to a minimum, but sometimes extra patients and emergencies mean that delays occur. We will keep you informed if this happens.