Changes of the Lid Fissure After Surgery on Horizontal Extraocular Muscles

To evaluate the effect of isolated medial and lateral rectus muscle surgery on eye lid position. Prospective, interventional case series. We recruited 36 patients with strabismus with surgery performed on one horizontal extraocular muscle only. The width of the lid fissure and the position of the upper and lower lids in relation to the pupil center were measured before and 3 months after surgery. Regression analysis was used to evaluate the surgical effect. Recessions induced a widening of and resections a narrowing of the lid fissure, mainly because of changes of the lower lid position. The effect was statistically significant (change in lid fissure width, = 0.13 × surgical dose in millimeters; r 2 = .35; P = .0001). Patients should be informed about changes in lid fissure width after operations on horizontal extraocular muscles. If adequately integrated into the surgical plan, this side effect may alleviate pre-existing interocular differences in lid configuration.