High Myopia-Associated Strabismus: Pathogenesis, Clinical Spectrum, and Surgical Management

Abstract

High myopia-associated strabismus, historically termed heavy eye syndrome, strabismus fixus, or convergent strabismus fixus, is a distinctive form of acquired restrictive strabismus that develops in eyes with substantial axial elongation. The posterior globe herniates through the superotemporal quadrant of the muscle cone, displacing the lateral and superior rectus muscles from their normal paths and producing progressive esotropia, hypotropia, and marked limitation of abduction and supraduction. High-resolution orbital magnetic resonance imaging over the past three decades has reshaped understanding of the condition, replacing earlier myopathic and mechanical-impingement theories with a pulley-displacement model rooted in orbital connective tissue biomechanics. Distinguishing this condition from the related but pathophysiologically distinct sagging eye syndrome has become central to accurate diagnosis and surgical planning. Surgical management has moved away from conventional recession-resection surgery, which tends to fail once dislocation is severe, towards muscle union and myopexy techniques that address the underlying anatomical derangement directly. The Yokoyama procedure and its many modifications, together with silicone band loop myopexy, muscle belly union surgery, and hemitransposition techniques, now form the backbone of management for moderate to severe disease. This review draws together current understanding of the epidemiology, pathogenesis, clinical spectrum, diagnostic evaluation, and surgical management of high myopia-associated strabismus, with attention to outcomes, complications, and the psychosocial burden the condition places on patients. Remaining uncertainties around patient selection, the value of adjunctive medial rectus recession, and long-term stability of surgical correction are discussed, along with directions for future research including standardised outcome reporting and imaging-guided surgical planning.