Influence of Cycloplegia on Axial Length Prediction Models in a Paediatric Sample.

CLINICAL RELEVANCE: Accurate axial length (AL) estimation is vital for monitoring myopia progression in children, especially in primary care where optical biometers are often unavailable. Prediction models with cycloplegic measurements may offer a reliable alternative.

PURPOSE: To assess the effect of cycloplegia on the accuracy and repeatability of several AL prediction models in a paediatric sample and to identify which models maintain minimal bias under both cycloplegic and non-cycloplegic conditions.

METHODS

Ninety-six children (mean age 12.5 ± 2.4 years) underwent repeated measurements of spherical equivalent refraction (SER), anterior corneal curvature (Kmean) and AL, pre- and post-cycloplegia, using the Myopia Master. Seven published prediction models incorporating SER, Kmean, age and sex were evaluated. Agreement, bias, limits of agreement (LoA), coefficient of repeatability (CoR), intraclass correlation coefficient (ICC) and regression analyses were used to assess performance and repeatability.

RESULTS

Cycloplegia induced a hyperopic shift (mean +0.79 D), most pronounced in emmetropic and hyperopic eyes. Measured AL and all models showed improved repeatability post-cycloplegia (measured AL CoR decreased from ~0.14 mm to ~0.09 mm; ICC > 0.99). Pre-cycloplegia, models overestimated AL (mean differences from -0.87 to -0.24 mm); these biases were reduced post-cycloplegia (mean differences from -0.56 to +0.10 mm). Models by Morgan et al., Queirós et al. and Lingham had the smallest bias (<0.10 mm) and narrowest LoA (<0.84 mm). Variation in SER accounted for ~97-99% of the change in predicted AL, while the Kmean contributed ≤1.2%.

CONCLUSION

Cycloplegic refraction significantly enhanced both accuracy and repeatability of AL prediction models in children. Models by Morgan et al., Queirós et al. and Lingham et al. performed best. Predictive models may be a valuable substitute in settings without access to optical biometers, provided cycloplegic measurements are used when possible.