C-scan ultrasonography in orbital diagnosis.

A C-scan imaging facility has recently been added to the ultrasonic system in use at Moorfields Eye Hospital, London. The technique is explained and typical C-scans are presented to demonstrate the normal orbital fat and optic nerve, together with selected pathological conditions in the orbit. The C-scan facility permits imaging of the orbital contents in the coronal plane. This coronal plane imaging, together with high resolution and sensitivity, makes this a useful technique for demonstrating orbital lesions and it is hoped helps in the accurate measurement of the diameters of the optic nerve along its length. The problems associated with C-scanning are discussed.