Monocular elevation deficiency associated ptosis misdiagnosed as simple congenital ptosis: management with Müller Muscle-Conjunctival Resection

<i>Purpose</i>: Monocular elevation deficiency (MED), formerly termed double elevator palsy, is a rare ocular motility disorder characterized by restriction of elevation in all gaze positions. Ptosis frequently accompanies MED but may be mistaken for simple congenital ptosis, potentially resulting in suboptimal surgical planning. While frontalis sling and levator resection are the most frequently employed techniques for MED-associated ptosis, these procedures carry a considerable risk of lagophthalmos and suboptimal cosmetic outcomes. To date, the use of Müller muscle - conjunctival resection (MMCR) in this context has not been described. <i>Methods</i>: We report the case of a 14-year-old girl initially diagnosed with congenital ptosis who was subsequently found to have MED. Ophthalmic examination revealed marked elevation deficit and mild hypotropia in the right eye, consistent with MED. As strabismus surgery was declined, ptosis correction was prioritized. Preoperative margin-reflex distance (MRD) measured 1.5 mm on the right and 4 mm on the left. A phenylephrine test demonstrated a partial positive response, increasing MRD to 2.5 mm. Considering the poor Bell's phenomenon and risk of exposure keratopathy, a 9-mm MMCR was performed under general anesthesia. <i>Results</i>: The surgery was completed without intraoperative or postoperative complications. At the one-month follow-up, eyelid contour and height were satisfactory, with the right MRD improved and symmetrical to the fellow eye. No lagophthalmos, corneal exposure, or epithelial keratopathy were observed. Functional and cosmetic outcomes were favorable, and the results remained stable at the 6-month and 1-year follow-up visits. <i>Conclusion</i>: This case highlights the diagnostic challenge of distinguishing MED-associated ptosis from isolated congenital ptosis and underscores the importance of comprehensive motility assessment. Traditional procedures for ptosis in MED, such as frontalis sling or levator resection, may predispose to lagophthalmos, particularly in patients with poor Bell's phenomenon. In contrast, MMCR offers a minimally invasive posterior approach that preserves the anterior lamella and reduces the risk of exposure keratopathy. To our knowledge, this is the first reported pediatric MED case successfully managed with MMCR. The procedure provided stable functional and aesthetic results, suggesting that MMCR may represent a safe and effective alternative in selected patients with MED when strabismus surgery is deferred.