Müller Muscle Conjunctival Resection: A Multicentered Prospective Analysis of Surgical Success

Purpose: This is a multicenter prospective cohort study investigating Müller muscle conjunctival resection success rates based on marginal reflex distance-1 (MRD1) and symmetry criteria. A secondary objective was to identify predictors of success. Methods: One hundred fifty-two patients with unilateral or bilateral blepharoptosis (229 eyelids) undergoing Müller muscle conjunctival resection were consecutively recruited from 2015 to 2020 at the Université de Montréal and University of California San Francisco. Ptosis was defined as MRD1 ≤ 2.0 mm or MRD1 > 1 mm lower than the contralateral eyelid. Patients were selected for Müller muscle conjunctival resection surgery if they demonstrated significant eyelid elevation following phenylephrine 2.5% testing. MRD1 success (operated eyelid achieving MRD1 ≥ 2.5 mm) and symmetry success (patient achieving an intereyelid MRD1 difference ≤ 1 mm) were evaluated for the patient cohort. Predictors of MRD1 and symmetry success were analyzed using multivariate regression analysis. Results: MRD1 success was achieved in 72.1% (n = 165) of 229 operated eyelids. Symmetry success was achieved in 75.7% (n = 115) of 152 patients. MRD1 before phenylephrine testing was the only statistically significant predictor of MRD1 success (odds ratio [OR] 2.69, p = 0.001). Symmetry following phenylephrine testing was the only variable associated with increased odds of symmetry success (OR 2.71, p = 0.024), and unilateral surgery (OR 0.21, p = 0.004), the only variable associated with reduced odds of symmetry success. Conclusions: Müller muscle conjunctival resection effectively achieves postoperative MRD1 and symmetry success. MRD1 before phenylephrine testing is the strongest determinant of MRD1 success. Neither a large rise in MRD1 with phenylephrine nor increasing tissue resection length adequately counterbalance the effect of a low MRD1 before phenylephrine. Unilateral surgery and the absence of symmetry following phenylephrine predict greater odds of symmetry failure.