This rare clinical picture characterized by intermittent unilateral or bilateralexophthalmos is caused byvaricose dilation of the orbital veins, such as canoccur following trauma or in Osler’s disease (polycythemia vera). Patients report protrusion of the eyeball of varying severity. Exophthalmos is usually unilateral and is especially prone to occur when the resistance to venous drainage is increased, as can occur when the patient presses, bends over, screams, or compresses the vessels of the neck. Occasionally the exophthal-mos will be associated with increased filling of the episcleral and/or conjunc-tival vessels. The disorder can be diagnosed in ultrasound studies using theValsalva maneuver. A differential diagnosis should exclude a fistula betweenthe carotid artery and cavernous sinus or an arteriovenous aneurysm, which is usually accompanied by a dramatic clinical picture with pulsation and increased intraocular pressure. In these clinical pictures, the ultrasound examination will reveal generalized dilation of the orbital veins. Surgical removal of orbital varices entails a high risk of damaging crucial delicate neu-rovascular structures in the orbital cavity. However, it may be indicated in rare cases such as cosmetically unacceptable exophthalmos or where symp-toms of keratoconjunctivitis sicca occur due to exposure that fails to respond to treatment.