Spherical Equivalent Refraction Versus Axial Length for Monitoring Childhood Myopia and Estimating Disease Risk: A Systematic Review and Meta-Analysis

TOPIC: To determine the relative merits of spherical equivalent refraction (SER) vs axial length (AL) as the primary measure for monitoring childhood myopia progression and predicting adult myopia-related pathology. CLINICAL RELEVANCE: Myopia prevalence is rising worldwide, but most patients only reach low-to-moderate myopia. Many guidelines emphasize AL over SER using fixed thresholds to define ``high risk'' (eg, ≥26 mm), yet a large proportion of myopia-related pathology occurs in eyes that never reach those lengths. METHODS: We conducted a systematic review and meta-analysis of population-based observational studies (≥200 eyes; PubMed and Embase searched from 1990 to July 2025) reporting AL and/or SER with demographics and/or retinal, cataract, or primary open-angle glaucoma (POAG) outcomes. Random effects meta-analyses with Hartung-Knapp adjustment were performed when k ≥ 3; other results were synthesized descriptively. Risk of bias was assessed with the Newcastle-Ottawa Scale and certainty of evidence with Grading of Recommendations Assessment, Development and Evaluation. RESULTS: Seventy studies met inclusion criteria. Normal AL varied strongly with age, sex, height, and ethnicity, whereas SER showed much weaker dependence. A small tail of emmetropes reached AL ≥26 mm. Retinal pathology rose steeply with longer AL (odds ratio [OR] 3.85 per +1 mm), implying risk ratio ≈25 at AL 26 mm relative to AL 23.6 mm (pooled gradient), but this long-eye threshold applied to