In this test, the eye is examined by ultrasound. The ultrasound uses high-frequency sound waves that are emitted and received by a hand-held instrument called a transducer. The sound waves travel through the eye.

Reflections (echoes) of the sound waves returning to the transducer form a picture of the structure of the eye. The precise size of the eye and any structures in the eye can be measured.

The test is usually done in the ophthalmologist’s office or the ophthalmology department. You usually sit in a chair. The eye will be numbed with anesthetizing drops. The transducer is placed against the front surface of the eye.

For the A-scan, you will be asked to look straight ahead. If a B-scan is performed, you will be asked to look in multiple directions. A lubricant placed on the transducer may run on your cheek, but there will be no discomfort or pain. The test takes about 15 minutes.

• Infant test or procedure preparation (birth to 1 year)
• Toddler test or procedure preparation (1 to 3 years)
• Preschooler test or procedure preparation (3 to 6 years)
• Schoolage test or procedure preparation (6 to 12 years)
• Adolescent test or procedure preparation (12 to 18 years)

The ultrasound helps evaluate the farthest part of the eyeball when you have cataracts or other reasons that make it hard to look into your eye. The test may help diagnose retinal detachment or other disorders when the eye is not clear and the ophthalmologist can not use routine examining equipment. An A-scan ultrasound measures the eye for the proper power of a lens implant before cataract surgery.

The test may reveal:

• Vitreous hemorrhage (bleeding into the transparent gel that fills the eyeball between the retina and the lens)
• Retinal detachment (separation of the retina from the middle coat of the eyeball),
• Tumors such as retinoblastoma (cancerous growth of retinal cells) or melanoma (cancerous growth of pigmented cells under the retina)
• Lesions in the orbit (the bony socket that protects the eye)
• Foreign bodies
• Inflammation