Fundus torsion in strabismus: measurement, clinical interpretation, and emerging imaging approaches

Fundus torsion is an important but underused anatomical marker in strabismus evaluation, particularly for cyclovertical disorders. Unlike subjective cyclodeviation testing, fundus-based assessment provides an objective reference based on retinal landmarks, though it remains influenced by image acquisition, head position, ocular anatomy, and measurement conventions. We synthesize the anatomical basis of ocular and fundus torsion, contemporary qualitative and quantitative assessment methods, and disease-specific evidence across superior oblique palsy, pattern strabismus, pediatric and adult strabismus, and surgical follow-up. The review emphasizes 3 clinically important issues: the frequent dissociation between objective fundus torsion and subjective cyclodeviation, the need for method-specific interpretation using reproducibility and minimal-detectable-change data, and the importance of avoiding isolated treatment decisions based on anatomical torsion alone. Recent optical coherence tomography-based and artificial intelligence-assisted approaches may improve measurement consistency and scalability, but current evidence supports their use as adjunctive tools rather than autonomous decision systems. Fundus torsion should therefore be interpreted within a multimodal clinical framework that integrates motility findings, sensory status, age, chronicity, fixation behavior, and surgical history. Treatment options include observation and symptom relief in selected patients, inferior oblique weakening for associated overaction, and torsion-directed surgery for persistent symptomatic excyclotorsion; comparative evidence remains limited. Prospective comparative treatment studies are a clinical research priority. Standardized acquisition protocols, explicit reporting conventions, age- and population-specific normative data, externally validated automated methods, and prospective studies linking torsional change to symptoms and functional outcomes are needed to strengthen the clinical utility of fundus torsion assessment.