Echographic diagnosis of dural carotid-cavernous sinus fistulas. I used standardized ophthalmic echography to identify specific abnormalities in four patients with low-pressure, low-flow dural arteriovenous malformations. In all of the patients, B-scan ultrasonography showed engorgement of the ipsilateral vertical vein. A-scan ultrasonography dynamically imaged rapid blood flow through the superior ophthalmic vein and enlargement of the culpable ocular muscles in patients with restrictive ophthalmopathy. The 30-degree test distinguished between venous engorgement of the optic nerve sheath and apical compression of the optic nerve by enlarged ocular muscles. 