MRI of the orbit with surface coils was performed in 40 patients. In 35 cases the findings were pathologic. The most frequent (n = 9) were malignant melanomas of the choroid, which were distinguishable from hemorrhages (n = 2) by the characteristic signal intensity pattern. MRI only offered advantages over CT in lesions of the orbital apex, the upper part of the orbit, and in the diagnosis of inflammatory processes. In most of the cases of orbital tumors, and particularly where there was involvement of bony structures, CT was equal to or better than MRI.

Arteriovenous malformation is a rare vascular disease of the orbit that has to be differentiated from arteriovenous fistulas (e.g., of the carotid sinus), arterial aneurysms, the varices and the angiomas. It develops in the presence of an underlying constitutional maldifferentiation of the vascular bed but usually only becomes manifest in early adulthood. Typical clinical signs are exophthalmos, often with pulsation and thrill; episcleral and conjunctival vascular congestion; secondary glaucoma; and, to varying degrees in the late stage, restricted movement with double images as well as functional losses. The therapeutic measures otherwise routinely applied for such vascular deformities - e.g., surgical excision or, even better, embolization - have to be handled with ease in the orbit, since these vascular convolutions are also supplied in all cases by the ophthalmic artery. Two typical cases are presented to illustrate the clinical picture, diagnosis, differential diagnosis, and treatment possibilities.