Axial elongation among Hong Kong myopic children and adolescents wearing single vision spectacles from a clinical setting

This retrospective cohort study investigates axial elongation in myopic children and adolescents wearing single vision spectacles, before and after the availability of proven myopia control spectacles. Electronic clinical records of patients aged 3-17 years who were prescribed single vision spectacle lenses between July 2012 and August 2013 (2012_13 cohort) and between July 2018 and August 2019 (2018_19 cohort) were analyzed. Follow-up duration ranged from 12 to 51 months, and axial elongation was normalized to a 12-month change. There were 330 and 165 patients in the 2012_13 and 2018_19 cohorts, respectively. The annualized axial elongation, expressed as mean (standard error), was 0.27 (0.01) mm for the 2012_13 cohort and 0.26 (0.01) mm for the 2018_19 cohort. In both cohorts, median annual axial growth was ≥ 0.40 mm at ages 3-5, ≥ 0.30 mm at ages 6-8, ≥ 0.20 mm at ages 9-10, ≥ 0.10 mm at ages 11-13, and < 0.10 mm at ages 14-17. Younger age was closely associated with faster annualized axial elongation, with each year of increase in baseline age results in a decrease in annualized axial growth by 0.04 mm. These findings serve as a useful reference for future myopia control trials to assess treatment efficacy.