Lana del Porto, Anne-Marie Hinds, Naz Raoof, Christen Barras, Indran Davagnanam, Gillian Adams
Purpose: To determine the extent of superior obli- que (SO) enlargement in Thyroid Eye Disease (TED) by comparing the cross sectional area of SO in TED to normal controls. To correlate SO enlarge- ment with orthoptic measurements including A- patterns and intorsion.
Methods: Retrospective review of demographic data and surgical outcomes for 66 TED patients treated for strabismus from January 2005 to January 2016. The cross sectional area of SO in 46 TED patients was compared to age matched controls on high reso- lution orbital Computed Tomographic (CT) using a standardised protocol.
Results: The SO cross sectional area in TED (right eye) was 250% larger than normal controls (9.3 mm2 [std 1.79] versus 23 mm2 [std 6.52]). 96% of TED patients demonstrated a SO cross sectional area greater than three standard deviations from the mean. A-patterns and intortion correlated with very signiftcant SO enlargement. The number of patients with torsion increased after primary rectus muscle surgery from 6.6% pre-op to 16% at three months post-op. Superior oblique surgery was performed in 0% at ftrst operation, 15% at second operation and 60% at third operation.
Conclusions: Superior oblique enlargement in TED is ubiquitous. Inferior rectus recession can ?unmask? signs of a tight SO such as intorsion. Consequently, the need for SO surgery increases with successive squint procedures. Strabismus surgeons should be aware of possible involvement of SO in TED and be prepared to address this surgically. Torsion and A- patterns should be measured in TED, although these may only be unmasked after rectus muscle surgery.