Exophthalmos may be defined as protrusion of the globe of the eye. It occurs in diseases of the thyroid, sinusitis, intracranial arteriovenous aneurysms, benign or malignant tumors (either primary or metastatic) of the orbit or within the cranial vault, thrombosis of the cavernous sinus, myopia, xanthomatosis, congenital malformations of the skull, Paget's disease and other diseases of the bones and hypertension. It rarely appears as "voluntary" exophthalmos. The discussion in this paper will be limited to the exophthalmos that occurs in certain types of disease of the thyroid.
The mechanism of the exophthalmos associated with spontaneous or experimentalthyrotoxicosis varies because of the anatomic peculiarities of different species of animals. In animals other than man stimulation of the cervical sympathetic nerves causes protrusion of the eyeball by contraction of Müller's muscle.1 Although in man Müller's muscle is vestigial, many studies have been made concerning the role of cervical sympathetic stimulation