Bidirectional Interaction Between Childhood Astigmatism and Myopia Development

Abstract

Astigmatism and myopia are among the most common refractive errors in childhood and have traditionally been considered distinct manifestations of abnormal refractive development. However, accumulating epidemiological, clinical, and experimental evidence suggests that their relationship may be bidirectional and dynamically influenced by ocular growth, visual experience, and individual susceptibility. Astigmatism may potentially affect myopia development by degrading retinal image quality, altering visual feedback, and modifying the signals involved in emmetropization and axial growth. Conversely, progressive myopia and axial elongation may influence astigmatic characteristics through changes in ocular geometry, corneal biomechanics, anterior–posterior corneal coupling, and internal optical compensation. In addition, genetic susceptibility, environmental exposure, age, and sex may modify the magnitude and timing of these interactions. Evidence from longitudinal and intervention studies further suggests that the association between astigmatism and myopia may vary according to astigmatic magnitude, axis orientation, baseline refractive status, and developmental stage. Nevertheless, substantial heterogeneity in study populations, measurement methods, and follow-up duration, together with the predominance of observational evidence, limits definitive conclusions regarding causality. Overall, current evidence supports substantial interaction rather than a clearly established direct causal relationship between childhood astigmatism and myopia. Concurrent monitoring of spherical and cylindrical refractive changes, together with axial-length assessment when feasible, may improve the identification of children at increased risk of refractive abnormalities. Further prospective longitudinal studies integrating refractive, biometric, corneal tomographic, optical, and biomechanical parameters are warranted to clarify the temporal and causal pathways linking astigmatism and myopia and to facilitate more precise strategies for prevention and individualized management of childhood refractive errors.