Diagnostic tests

While at Moorfields, your child may need to undergo a number of tests to help the doctors understand their eye condition. Some of those tests are desrcibed below.

Fluorescein angiography

Fluorescein angiography is carried out to help doctors diagnose problems with the eye. Your child’s eyes will be dilated and a small amount of dye injected into the arm. Local anaesthetic will be applied to the arm in order to numb the area.

Electrodiagnostics

Electrophysiological tests are carried out to help the doctors understand the way brain and eye function together. Electrophysiology helps the doctors to distinguish between different eye disorders that may have the same symptoms, and also helps them understand if an eye condition is changing or stable.

Phlebotomy

Phlebotomy is where a blood sample is taken. Local anaesthetic cream will be applied to your child's arm 30 minutes before the sample is taken.

B-scan-diagnostic ultrasound examination

Examinations take just a few minutes to complete and are painless. No anaesthetic is required.

Children are examined while seated and babies or young infants are generally examined while cradled on a parent’s lap but may be examined in a portable car seat / buggy.  Ideally the head should kept be as still as possible.

A small wand (probe) is smeared with a liquid gel and moved over the closed eyelid. The probe emits high frequency pulses of sound (ultrasound pulses) into the eye and surrounding tissues. In the time intervals between emission of ultrasound  pulses,  the probe receives any echoes scattered back towards it, converts the echoes into electrical signals and displays them on a screen in the form of cross-sectional images of the eye, in real-time.

The physicist or ophthalmologist performing the scan can make diagnoses from the moving images on the screen. Selected images are stored digitally.

Measurements of eye structures are generally made from any stored images once the examination is over. A report will be typed immediately following the examination and given to parents to take back to the referring ophthalmologist.

Dilating drops

When you come to the hospital, it may be necessary to look at the back of your child’s eye. In order to do this we will need to put some eye drops into their eyes, which will make the pupil (black part of the eye) bigger. This does not hurt your child but may sting a bit while the drops are going in, and your child will have to keep still while we do this. The nurses are very experienced in putting in eye drops and we use different ways of doing this, using toys, bubbles, etc, and involving members of the play team. It can take anywhere between 20-30 minutes for the drops to work and your child’s eyes to be dilated (get bigger). For dark eyes it will be necessary to put more drops in and can take up to 60 minutes.

The drops can take up to several hours to stop working and occasionally there can be small effects the following day. If your child is more active than usual or a little flusher (red) after these drops this is normal and please do not worry. 

Refraction

This test measures whether your child is long-sighted or short-sighted. Your child’s eyes will need to be dilated using the eye drops as described above.  In order to complete the test, the optomotrist will use different types of lenses which are held up close to the eyes and shine a little light in each eye. The optomotrist will try to use a trial frame on the child’s eyes and insert lenses into the frame in order to determine an accurate result. This is like a pretend pair of glasses and the optomotrist will put lenses onto the frames while looking into the back of your child’s eye with a light. They will then be able to tell you what strength of glasses your child needs to wear.

Once your child is old enough, a refraction test will be able to be performed without using the eye drops – this is called a subjective refraction.