A clinical–biomechanical model of combined resection–recession surgery of the inferior rectus muscle in incomitant strabismus

PURPOSE: To develop a simplified clinical-biomechanical framework for two observations in inferior rectus resection-recession surgery: the shortening-to-recession ratio (S/R, where S is the resection or shortening amount and R is the recession amount) is generally below unity, and satisfactory primary-position alignment may coexist with postoperative infraduction limitation. METHODS: A conceptual biomechanical framework was developed based on two distinct consequences of inferior rectus recession: alteration of alignment-related force balance and alteration of anterior muscle-globe geometry. Resection was considered to compensate primarily for the alignment-related component, whereas recession was assumed to influence both static alignment and dynamic force transmission. Published clinical case series were used for contextual comparison; no systematic review or pooled analysis was performed. RESULTS: The framework separates the alignment-related effect of recession from the associated alteration of anterior muscle-globe geometry, explaining how satisfactory primary-position alignment can coexist with postoperative infraduction limitation. The predominantly subunitary S/R ratios reported in clinical series are consistent with this interpretation and support the mechanical plausibility of non-1:1 compensation; optimal surgical dosage remains empirical. CONCLUSIONS: Inferior rectus resection-recession surgery addresses two partially independent biomechanical objectives: restoration of primary-position alignment and preservation of dynamic downgaze function. This framework helps interpret both commonly used subunitary surgical ratios and the dissociation between alignment and function observed in practice.