Spherical Equivalent Progression Estimated by Axial Length Changes

The ratio of the change in spherical equivalent (SE) and change in axial length (AL) (ΔSE/ΔAL) varies with age and refractive error in children, but can be used to estimate SE progression, according to research published in Ophthalmic and Physiological Optics. 

Researchers included 710 children and adolescents (mean age 9.41±2.80 years, 55.77% boys, 37.32% with myopia) in the analysis. Participants underwent comprehensive ophthalmic exams including SE, AL, and corneal curvature measurements at baseline and at 1-year follow-up.

After constructing a linear model, the investigators determined that the mean 1-year ΔSE and ΔAL were 0.61±0.40 D and 0.33±0.22 mm. The ΔSE and ΔAL gradually decreased with age (P <.001) and age and refractive status were independently associated with ΔSE/ΔAL after adjustment for covariates (age:  ̂β=0.04, P <0.05; myopia vs non myopia:  ̂β=0.28, P <0.05), according to the report. A general linear model analysis was used to create formulas for predicting age-specific ΔSE/ΔAL in patients with myopia (ΔSE/ΔAL=1.74+0.05*age) and children who were not myopic (ΔSE/ΔAL=ΔSE/ΔAL = 1.33+0.05*age). Using these formulas, the report noted ratio increases of 2.06 D/mm in 6 year olds to 2.59 D/mm in 16 year-olds with myopia and an increase from 1.65 D/mm in 6 year-olds without myopia to 2.18 D/mm in 16-year-olds without myopia. 

Researchers highlight the clinical implications of the age-specific ΔSE/ΔAL ratio including, “detect[ing] the rate of SE progression based solely on AL data, identify[ing] children who are experiencing rapid myopia progression and refer[ring] them for further examination and treatment.”

Study limitations include a short duration of follow-up, an unbalanced age distribution, and a failure to obtain other biometric parameters. 

Reference

Liu S, He X, Wang J, et al. Association between axial length elongation and spherical equivalent progression in Chinese children and adolescents. Ophthalmic Physiol Opt. Published online June 29, 2022. doi:10.1111/opo.13023