What is it?
Ultrasound is sound with a very high pitch. So high that it cannot be heard by people, or even by dolphins or bats.
A probe resembling a small wand, and emitting ultrasound, is used to examine the eye. The ultrasound “bounces off” the eye’s internal structures to create echoes which then return to the wand. A computer uses the echoes to form a picture that the doctor performing the scan can interpret.
When is this test carried out?
Usually an ophthalmologist only needs light to examine an eye. But this can prove difficult if there is blood in the eye, or a cataract. In such cases an ultrasound test is performed instead. Ultrasound is also used to measure an eye’s length.
What does it offer?
An ultrasound test will give the ophthalmologist vital information to help them decide the best way to treat the eye.
What happens during the test?
Examinations take just a few minutes to complete and are painless, with no anaesthesia required. Ideally the head should kept be as still as possible.
Children are examined whilst seated. Babies or young infants are generally examined whilst cradled on a parent’s lap but may be examined in a portable car seat or buggy.
A probe is smeared with a liquid gel and moved over the closed eyelid. The probe emits pulses of ultrasound into the eye and surrounding tissue. During the brief intervals of time between each pulse, the probe receives any echoes which scatter back towards it. The echoes are converted into electric signals which are displayed on screen as real-time images of the eye in cross section.
The operator performing the scan can make diagnoses from the moving images on the screen and digitally store any selected images.
Measurements of eye structures are generally made from any stored images once the examination is over. A report is produced immediately following the examination for patients to take back to the referring ophthalmologist.