Thyroid orbitopathy: an update.

Two typical findings in thyroid orbitopathy have traditional explanations which are not wholly acceptable in many cases of the disease. Eyelid retraction is attributed to superstimulation of Mueller's palpebral muscle, while vertical muscle imbalances are attributed to preferential involvement of the vertically acting muscles in the myositic process. Clinical and experimental ultrasonographic evidence recently gathered indicates that endocrine orbitopathy is panmyositis involving all of the muscles of the orbit simultaneously. In light of this improved understanding of the muscular involvement in this disease, we propose alternate explanations for the signs and symptoms of thyroid orbitopathy which are based upon physiologic, anatomic, and pathologic facts.