Relationship Between the Severity of Blepharoptosis and Pathological Changes in the Levator Aponeurosis

PURPOSE To investigate the relationship between the severity of involutional blepharoptosis and microscopic degenerative changes of the levator aponeurosis, focusing on the proportion of fibrous tissue and fatty replacement. METHODS Fifteen patients with involutional blepharoptosis (30 eyelids) undergoing levator resection were enrolled. Levator aponeurosis specimens were analyzed histologically using Elastica–Masson staining. The proportion of collagen-rich fibrous tissue (fibrous area index) and fatty replacement (fat area index) were quantified. Correlations with margin reflex distance 1 (MRD-1) and levator function (LF) were assessed using linear mixed-effects models. RESULTS Univariate linear mixed-effects model analysis showed a significant positive association between levator function (LF) and margin reflex distance-1 (MRD-1) (P < 0.001). The fibrous area index was significantly positively associated with both MRD-1 (P = 0.02) and LF (P = 0.01). Conversely, the fibrous area index showed a significant negative association with the fat area index (P = 0.01). Age was significantly negatively associated with LF (P = 0.04), while male sex was associated with a higher fibrous area index (P = 0.04). In the multivariate analysis, LF was independently associated with the fibrous area index (P = 0.002), age (P = 0.03), and sex (P = 0.04). MRD-1 was significantly associated with LF (P < 0.001), whereas it showed no significant association with histological parameters. CONCLUSIONS Degenerative remodeling of the levator aponeurosis, characterized by loss of fibrous tissue and fatty replacement, is closely associated with LF but not with MRD-1. These findings suggest that LF and eyelid position reflect distinct pathophysiological aspects of involutional blepharoptosis.