To identify levator palpebrae superioris enlargement in thyroid eye disease (TED)-related upper eyelid retraction (ULR).
Retrospective case–control. Subjects included 50 consecutive patients with unilateral thyroid eye disease-related ULR ≥ 2 mm and no previous eyelid surgery. The contralateral side was used as control. Clinical information was recorded from charts. CT scans were assessed by investigators blinded to the clinical data. A prediction of retracted side was made based on CT scan appearance and on basis of measured levator palpebrae superioris cross-sectional area at 2 defined points. Statistical analysis determined correlation between levator palpebrae superioris size and presence of ULR. The study was approved by the institutional ethics committee.
Side with ULR predicted from CT scan review in over 85% of cases. Mean cross-sectional area of levator palpebrae superioris on retracted side was significantly larger than nonretracted side at 2 separate sites. Levator palpebrae superioris area was larger on retracted side compared with nonretracted side in over 85% of subjects. More than 30% of subjects had no enlargement of other extraocular muscles. Only 6% of patients had enlargement of the ipsilateral inferior rectus muscle.
Levator palpebrae superioris enlargement from inflammation or scar is a factor in thyroid eye disease-related ULR. Upper eyelid retraction can be predicted from CT scan appearance in over 85% of cases. Ipsilateral inferior rectus enlargement is rare. Levator palpebrae superioris is the most commonly targeted muscle in thyroid eye disease.