Histology of Müller's muscle observed in quiescent Graves' orbitopathy.

OBJECTIVE: Histologic examination of Müller's muscle (MM) in patients with clinically significant upper eyelid retraction secondary to Graves' orbitopathy (GO).

DESIGN: Prospective, single-blinded, comparative experimental study at a single institution.

PARTICIPANTS: Patients from a single San Francisco Bay Area practice (RZS).

METHODS: Consecutive patients with upper eyelid retraction secondary to GO who underwent surgical correction by transcutaneous mullerectomy were recruited between January and December 2011. An equal number of control MM specimens were gathered in consecutive patients undergoing conjunctivo-MM resection for ptosis correction. A total of 10 specimens in each group was available for analysis. The proportion of fat and fibrosis, as well as inflammatory markers, was studied and graded in both the study and the control group by a masked pathologist. These data were compared between groups using the Student t-test.

RESULTS: No significant difference between the 2 groups of MM specimens was detected.

CONCLUSIONS: Patients with quiescent GO with clinically significant eyelid retraction exhibit normal MM histology.