Purpose: To investigate the relationships between pre-operative marginal reflex distance (MRD), tissue resection length, phenylephrine response, and change in MRD with surgery for a cohort of individuals undergoing Muller's muscle conjunctival resection (MMCR) surgery.
Methods: All cases of MMCR surgery performed over a 13-year period at a single institution were screened for entry. Individuals with adequate photographic documentation and follow up were included. Patients with previous or concurrent upper eyelid, orbital or eyebrow disease of surgery were excluded. Marginal reflex distance (MRD) was calculated based on photographs utilizing public domain software. Data was plotted for inspection and appropriate statistical tests were performed.
Results: During the study period 198 eyes fit criteria for analysis. A loose association between tissue resection length and change in MRD with surgery was found (r = 0.176, p < 0.05); this relationship was not significant in ANOVA analysis (p = 0.367). There was a strong association between MRD change with surgery and pre-operative MRD (r = 0.498, p < 0.01). Approximately 28% of the sample responded to 2.5% phenylephrine drop instillation with a greater than 2 mm increase in MRD. The response to phenylephrine was strongly associated with pre-operative MRD (r = -0.441, p < 0.01). A regression on change in MRD with surgery with tissue resection, phenylephrine response >2 mm and pre-operative MRD as variables revealed a model with pre-operative MRD as the only significant predictor (p < 0.01).
Conclusion: Tissue resection length and phenylephrine response play small roles relative to pre-operative MRD in the determination of change in MRD with MMCR surgery.
Keywords: Eyelids; Muller’s muscle-conjunctival resection; ptosis.