Angiography of the eyes using fluorescein or indocyanine green (ICG)

There are several different types of angiography. This leaflet focuses specifically on angiography of the eyes using fluorescein and ICG. 

Vision – or being able to see – involves various parts of the eye. 

First, light enters the eye through the pupil. The tiny muscles attached to the lens squeeze or relax to focus the light onto the retina. The retina is the lining at the back of the eye. At this point, the image is upside down. 

Signals from the retina then travel down the optic nerve to the brain, which interprets them and automatically turns the image the right way up again.

The retina is supplied with blood and oxygen through a network of tiny blood vessels. Any damage to the blood vessels affects how the retina works, can producing a ‘blind spot’ or a change in vision over that area

Angiography is a way of taking a picture of the blood flow around the eye. 

It is used to help doctors confirm or rule out certain eye conditions or monitor eye treatment. 

Fluorescein and ICG are dyes that are used in angiography to help make the blood more obvious – they help make the pictures of the blood flow clearer. 

Fluorescein angiography is a way of looking at these blood vessels to see if there are any abnormalities or damaged areas.

Behind the retina lays the choroid, which nourishes the retina and cleans up debris. ICG angiography is a way for us to see how blood is flowing in the choroid and retina, to help us diagnose, treat or manage conditions affecting these areas. 

Fluorescein glows under blue light. When fluorescein is swallowed or administered, it travels to the blood vessels supplying the retina at the back of the eye. This can take up to 30 minutes.

When a blue light is shone into the eye, the blood vessels glow so are easier to see and photograph. 

ICG is a similar type of dye, but it glows at a different wavelength (colour) to fluorescein. This allows the images to be taken at deeper layers, which is particularly useful for looking at areas of the eye like the choroid.

Once you have checked into Eye Clinic, the clinic assistants will weigh and measure your child. We will then calculate the amount of dye needed according to your child’s weight.

A member of the team will then explain about the test and answer any questions you may have. They will ask you to give your permission for the test by signing a consent form.

The clinic assistant may put some drops in each eye – these make the pupil at the front of the eye widen so more light can enter. This helps make the photographs more accurate.

To administer the dyes there are two methods. Which method your child has will depend on the type of angiography they are having, and their age and ability.  The two methods are: 

Oral fluorescein: 

We will give your child a drink of ice-cold juice or squash which contains the dose of fluorescein dye. 

The fluorescein does not taste very nice, so we suggest they drink it in one go, usually with a straw. We will give them another drink afterwards to take away the taste. 

If you are having oral fluorescein please do not have any breakfast before your test so that the dye can show up quicker.

Intravenous fluorescein or ICG:

We will place a very small plastic tube (cannula) into a vein on the arm to administer the dyes. We can use a spray (or numbing cream) to make this more comfortable. 

This method is usually chosen if we:

• Need to see how quickly the blood is flowing into the eye – the dye shows up in the eye much faster in this method.
• If an ICG dye is needed – ICG cannot be given by mouth. 

After any dyes are given, the imaging team will take a series of photographs over the next 30 minutes, as the dye travels to the blood vessels in the eye.

After we have completed the imaging, you will usually have an appointment with the clinician responsible for your care to discuss the results. 

To ensure that there are no adverse reactions, we advise waiting in the department for 30 minutes after the test, so we can make sure your child has not an allergic reaction to the dye. 

Please note, the person bringing your child for the test should have ‘Parental Responsibility’ for them. Parental Responsibility refers to the individual who has legal rights, responsibilities, duties, power and authority to make decisions for a child. If the person bringing your child does not have Parental Responsibility, we may have to cancel the test.

If your child or a close relative has ever had a severe reaction to injected dyes, please tell us as soon as possible. We may need to use a different method. 

Please also let us know if your child has: 

• Uncontrolled hypertension 
• Heart or respiratory failure 
• Kidney or liver disorders

Oral fluorescein can stain the teeth so we will give your child a straw drink from. Staining is temporary and will fades with good tooth brushing over the next few days.

The skin may discolour, a few minutes after taking fluorescein. It may turn a yellow colour or appear more orange on brown or black skin tones. This will gradually fade over 6–12 hours as the dye is absorbed by the body. The dye is removed by the kidneys and passes out of the body in urine (wee). This means that your child’s wee may glow for 24–36 hours after the angiography. These effects are harmless and temporary.

Rarely, some people have a severe allergic reaction to fluorescein or ICG. Signs of a severe allergic reaction include:

• skin rashes and itching
• high temperature
• shivering
• redness of the face – this may be harder to see on brown or black skin tones. tones
• feeling dizzy 
• headache
• shortness of breath
• chest pain. 

If you think your child is having an allergic reaction, and are still in hospital, tell the clinical team straight away. 

If you have left the hospital, please contact your GP or A&E department urgently. Allergic reactions usually happen soon after administration of the dyes, so the risk of an adverse effect after you leave is much lower.

Milder symptoms of an allergic reaction can include sneezing, itching and a high temperature. The effects of a mild allergic reaction are usually temporary and often don’t require treatment, but you can tell any of the team looking after you about symptoms and we will do our best to help. 

If the dye leaks outside the vein it may cause temporary pain. This can be relieved by cold compression – either a towel soaked in cold water or an ice pack held firmly on the injection site. If the injection site remains painful or causes you concern, please seek medical advice from your GP or attend A&E.

We will monitor your child for around 1 hour after they have been administered any dyes. If they show any signs of an allergic reaction, please let the doctor or nurse know immediately. 

Your child should drink plenty of fluids after the test. This will help their body flush the dye out of their system.

Do not be alarmed if their urine is a different colour or glows, this shows that the dye is leaving their body as expected.

Your child’s skin may discolour in the hours after the test (see above)– again this is just the dye travelling through your child’s body. This will disappear over the next few hours.

We will make sure that the results are ready in time for your next appointment with the eye doctor, even if this is the same day as the test.

If you have any questions about the use of dyes for ophthalmic imaging, please contact the Head of Ophthalmic Imaging, Dr Oliver Marmoy, using the details below:

Phone: 020 7405 9200 extension 7557

Email: oliver.marmoy@gosh.nhs.uk