The ultrasound uses high-frequency sound waves that travel through the eye. Reflections (echoes) of the sound waves form a picture of the structure of the eye. The test takes about 15 minutes.

There are two types of scans

A-SCAN

• You will usually sit in. a chair and place your chin on a chin rest. You will look straight ahead.
• A small probe with some oil on it is placed against the front of your eye.
• The test may also be done with you lying back. With this method, a fluid-filled cup is placed against your eye to do the test.

B-SCAN

• You will be seated and you may be asked to look in many directions. The test is usually done with your eyes closed.
• A gel is placed on the skin of your eyelids. The B-scan probe is gently placed against your eyelids to do the test.

How to Prepare for the Test?

No special preparation is needed for this test.

How the Test Will Feel?

Your eye is numbed, so you shouldn't have any discomfort. You may be asked to look in different directions to improve the ultrasound image or so it can view different areas of your eye.

A lubricant placed on the ultrasound wand may run on your cheek, but you won't feel any discomfort or pain.

Why the Test is Performed?

Your doctor may order this test if you have cataracts or other eye problems.

An A-scan ultrasound measures the eye to determine the right power of a lens implant before cataract surgery.

A B-scan is done to look at the inside part of the eye or the space behind the eye that can't be seen directly. This may occur when you have cataracts or other conditions that make it hard for the doctor to see into the back of your eye. The test may help diagnose retinal detachment, tumors, or other disorders.

Normal Results

For an A-scan, measurements of the eye are in the normal range

For a B-scan, the structures of the eye and orbit appear normal

What Abnormal Results Mean?

A B-scan may show:

• Bleeding into the clear gel (vitreous) that fills the back of the eye (vitreous hemorrhage)
• Cancer of the retina (retinoblastoma), under the retina, or in other parts of the eye (such as melanoma)
• Damaged tissue or injuries in the bony socket that surrounds and protects the eye (orbit)
• Foreign bodies
• Pulling away of the retina from the back of the eye (retinal detachment)
• Swelling (inflammation)

Risks

To avoid scratching the cornea, do not rub the numbed eye until the anesthetic wears off (about 15 minutes). There are no other risks.