How Ophthalmic Scanning of the Eye is done

The ultrasound is widely used for the diagnostics scanning of the eye. A-scan and B-scan modes of display are used in ophthalmic scanning. The transducer is placed directly over the eye of the patient while performing ophthalmic scanning. The high frequency sound waves that travel through the eye and the reflections (echoes) of these waves can form a picture of the structure of the eye.

In a scan, the transducer is positioned so that the ultrasonic beam passes through a chosen ocular meridian. Pulses of high frequency sound are transmitted from the transducer into the eye via the coupling medium. In the time interval between pulses, echoes are received by the same transducer and recorded as spikes on the oscilloscope. The height of the spikes indicates the size of the echo while the position of the spike along the horizontal axis indicates the time of receiving the echo. The nature of abnormalities gives rise to echoes that may be suggested by the size, extent and movement of the echoes.

In B-scan, echoes are plotted as dots instead of spikes and the brightness of the dots indicates the size of the received echoes. The transducer is moved to several positions about the eye and a whole series of intensity registrations are plotted.

You can also read: Ultrasound Scanning Techniques

The Ophthalmic Scanning Show:

• Cancer cells in the retina or other parts
• Bleeding into clear gel that fills the eyeball between the retina and lens
• Damaged tissues in the boney socket
• Separation from retina
• Swelling in the eye
• Sight disorder
• Intraocular power
• Any foreign body in the eye

When the light conducting media in the eye are opaque making ophthalmoscopy impossible, then ultrasound scanning is the most practical and rapid method of obtaining images of the posterior segment, yielding information for diagnosis.