Evaluation of unilateral exophthalmos with ultrasonography: analysis of 258 consecutive cases.

Ultrasound examination has emerged as a valuable technique for defining soft tissue abnormalities of the eye and orbit. As high frequency sound waves (5 to 20 megahertz) are projected through soft tissues, echoes are produced at tissue interfaces. These echoes are displayed on oscilloscopes as either one-dimensional amplitude spikes (A-mode ultrasonography), or as dots integrated into a two-dimensional image representing a thin section through the entire orbit (B-scan ultrasonography). A-mode indicates tissue substance, while B-scan illustrates tissue morphology. With this technique, orbital tumors are clearly distinguished in terms of their location, size, and configuration, as well as the basic tissue type (cystic, solid, angiomatous or infiltrative). Other orbital processes are defined by ultrasonography also, including inflammatory conditions such as diffuse pseudotumor or cellulitis, congestive conditions such as dysthyroid exophthalmos, and orbital hemorrhage. Intracranial and vascular etiologies of exophthalmos have no specific ultrasound signs. In a series of 258 consecutive patients with unilateral exophthalmos examined with ultrasonography, diagnosis of tumor was made in 26 percent (66 cases). Overall accuracy of orbital tumor diagnosis by ultrasonography was 94 percent in this series. Tumor localization, configuration, and extent indicated by the test aided in selecting surgical approaches. Other patients in the series were diagnosed ultrasonically as a variety of other entities, mostly inflammatory and dysthyroid exophthalmos. Normal ultrasound studies were found in 19 percent. None of these patients had subsequent diagnosis of tumor. Diagnostic ultrasonography is capable of detecting orbital tumors and distinguishing them from inflammatory, congestive, and other causes of exophthalmos with a high degree of reliability. The test is painless, well tolerated, non-invasive, and non-toxic. It now has a prominent role in evaluation of any patient with exophthalmos.