Quantifying interocular asymmetry of axial elongation in childhood myopia: metric framework, prevalence, and age-related dynamics — analytical dataset and code

This deposit accompanies a methodological study introducing and characterising the Cumulative Relative Asymmetry Index (CRAI) — a novel approximately scale-invariant metric for quantifying interocular asymmetry of axial elongation in paediatric myopia. The metric is defined at the interval level (Relative Asymmetry Index, RAI) and aggregated at the patient level (CRAI), complemented by an annualised Absolute Asymmetry Index (AAI). The deposit contains the anonymised patient-level dataset patients_anonymised.csv (n = 267 children, ages 5–16 years, 913 follow-up intervals), the interval-level dataset intervals_anonymised.csv, the Python reference implementation crai_metrics.py, and a complete analysis pipeline analysis_pipeline.py reproducing the principal numerical findings. Data collection. Clinical records were collected during routine ophthalmological care between 2015 and 2026 in Barnaul, Russian Federation. Dataset columns include CRAI_percent, AAI_annual_mm_per_year, net_AL_change_rate_mm_per_year, age_years_at_first_visit, sex, followup_duration_years, and n_valid_intervals (full schema in README.md). Key findings reproducible from this deposit: 15 % of children with progressive myopia exhibit statistically detectable interocular asymmetry of axial elongation (AAI exceeding their patient-specific Minimal Detectable Change at 95 % confidence, median MDC₉₅ 0.162 mm/year, range 0.024–0.395 across patients), and 13.9 % demonstrate pronounced asymmetry (CRAI > 50 %), where the slower-progressing eye accumulates axial length at no more than half the rate of the faster-progressing eye. Beyond these strictly defined groups, approximately 70 % of patients display a non-minimal asymmetric component (CRAI > 15 %). Convergent evidence supports the pronounced-asymmetry signal: within the pronounced stratum, no patients fall below the patient-level measurement noise floor (~0.067 mm/year), and 65 % exceed their patient-specific MDC₉₅ — providing convergent support against measurement uncertainty. Median CRAI 22.7 %, median annualised AAI 0.073 mm/year, category prevalence 30.7 % / 55.4 % / 13.9 % (Minimal / Moderate / Pronounced). CRAI is positively associated with age across the paediatric age range (Spearman ρ = +0.28, p < 0.001), persisting after adjustment for the overall net AL change rate (partial ρ = +0.25, p < 0.001), while the overall net AL change rate decreases approximately three-fold across age strata. CRAI is statistically independent of the overall net AL change rate after age adjustment (partial ρ = −0.08, p = 0.20), consistent with approximate scale invariance — making it applicable in cohorts with widely different overall progression activity. Reproduction. Run python analysis_pipeline.py against the deposited datasets to reproduce Table 1 (cohort characteristics), Table 2 (CRAI category prevalence with Wilson confidence intervals), age-stratified dynamics (Table 3 in the manuscript), and the noise-floor and patient-specific MDC₉₅ simulation. Requires numpy, pandas, scipy only. Version 3.1 (July 2026). Corrected the derivation of the patient-level noise floor and MDC₉₅. Earlier versions applied MDC₉₅ = 1.96 × SEM with a median-of-3-intervals SEM of σ/√3, giving a single cohort threshold of ≈ 0.118 mm/year; that expression is not valid for the median of the absolute interocular difference (its null is not centred at zero) under interval-specific annualisation. The noise floor and a patient-specific MDC₉₅ are now obtained directly from the null distribution of the statistic by Monte-Carlo simulation over each patient's observed interval structure (intervals_anonymised.csv, new in this version). Resulting benchmarks: noise floor 0.067 mm/year; MDC₉₅ median 0.162 mm/year; 15 % of patients above their own MDC₉₅ (previously reported as 22 %). Category prevalence, CRAI/AAI values, correlations, and all hypothesis tests are unchanged. Version 3.0 (May 2026). Recalibrated to canonical raw data snapshot of 23 May 2026. Cohort updated from n = 256 to n = 267 patients (913 valid intervals; previously 904). The annualised rate variable is reformulated as the signed net AL change rate (preserving the directional distinction between net axial elongation and net axial shortening driven by choroidal thickening response to therapy) and renamed from mean_annual_AL_growth_mm_per_year to net_AL_change_rate_mm_per_year. Metric definitions (RAI, CRAI, AAI) and category cut-offs (15 / 50 %) are unchanged from Version 2.0. Version 2.0 (May 2026). Revised principal category cut-offs from 15 / 45 % to 15 / 50 % on principled grounds — 15 % serves as a statistical noise filter while 50 % has a direct biological interpretation. Dataset and metric definitions unchanged from Version 1.0; only default category thresholds in the code (categorize_crai() defaults and reproduce_table_2()) updated.