Muller's muscle fibrosis is a possible predictive factor in the outcome of Muller's muscle-conjunctival resection.

Background: The purpose of our prospective study is to investigate the histopathology of Muller's muscle extracted after Muller's Muscle-Conjunctival Resection (MMCR) and to find the relationship between histopathological findings and the outcomes of ptosis surgery.

Methods: Forty-seven patients with mild to moderate ptosis underwent MMCR surgery and pathological samples including conjunctiva and Muller's muscle were stained with Hematoxylin and Eosin (H/E) and Masson trichrome. The degree of muscle fibrosis and hypertrophy were evaluated.

Results: The results indicated that an increase in the severity of fibrosis (for example, increase from mild to moderate), increases the 1 mm correction effect by 0.027 (CI = 0.002-0.052 and p-value = 0.033). There is no association between the 1 mm correction effect (p-value = 0.67), ptosis correction (p-value = 0.60), and post-operation difference between ptotic and normal eye (p-value = 0.90) with Muller's muscle hypertrophy. Also, there is no statistically significant association between Muller's muscle hypertrophy and 1 mm correction effect, ptosis correction, and post-operation difference according to the type of pathogenesis (aponeurotic; p-value = 0.123, congenital; p-value = 0.286, horner syndrome; p-value = 0.667).

Conclusions: Following the increase in Muller's muscle fibrosis, the ptosis correction effect of MMCR surgery increases, but the presence or absence of hypertrophy of Muller's muscle is not correlated to the outcomes of surgery.