Ultrasound of the eye (A+B scan)

What is ultrasound of the eye?

The eye is a globe filled with a clear gel (the vitreous) that maintains the shape of the eye. The ultrasound is an easy to use modality for visualization of ocular pathology and anatomy. Sound waves are generated and reflected back to the probe, resulting in electrical impulses that are translated into an image or other data. There are two main types of ultrasounds used in ophthalmologic practice currently, A-Scan and B-scan. In A-scan, sound waves are generated and converted into spikes that correspond with tissue interface zones. In B-scan, or brightness amplitude scan, sound waves are generated and the data collected by the transducer produces a corresponding image.

Why is the test performed?

The test is performed to obtain information, diagnose and follow up on different conditions of the eye. The A scan is used to obtain globe length (axial length) in order to calculate corrective intraocular lens power requirements. The B scan is used to visualize the posterior segment of the eye (the retina and choroid). B scan uses include the measurement of tumors including choroidal melanomas, visualization of lens dislocation, and detection of retinal detachment. The benefits of ultrasound include improved visualization of structures obscured by opaque substances, such as dense cataracts or vitreous hemorrhage. Second, real time information is available to the practitioner regarding conditions such as retinal detachment. Finally, ultrasound is safe, does not expose the patient to radiation, is widely accessible, and is low cost.

How is the test performed?

The test is very simple and fast. It takes few seconds to perform the test on each eye. It is noninvasive and no injection is needed. In some cases, a numbing eye drop may be administered for A-scan test. During the test, you will sit in front of the machine. During B scan ultrasound the doctor or technician will apply the ultrasound probe over your eyelids with your eyes closed so no direct contact on the eye is applied. The equipment will then scan your eye. Scanning takes few seconds.