There is sufficient evidence that OK and HAL lenses are safe and effective options for myopia control,
4 whereas the reports on whether their effects differ remain limited. Yu et al.
25 found that corneal refractive therapy (CRT) OK lenses and HAL were similarly effective in managing myopia from −1.00 to −2.00 D over one year. However, CRT OK lenses demonstrated a superior effect in retarding axial elongation relative to HAL for individuals with SER values of −2.00 to −3.00 D. Inconsistent with these, the present study demonstrated that children with initial myopia below −3.00 D in the HAL group showed significantly slower axial elongation than those fitted with SPOK and EOK lenses. The different effects on myopia control reported by the two studies may be attributed to several factors. First, the children in the study by Yu et al.
25 were older on average (10.3 years) than those in the present study. Second, the mean axial elongation of the control group in the study by Yu et al.
25 (0.35 mm) was lower than the 0.45 mm observed in the SVL group of the present study, suggesting inherently slower axial growth in their participants. Third, Yu et al.
25 used CRT lenses, whereas this study used vision-shaping treatment lenses; previous studies have reported different myopia control effects for these two types of lenses.
38,45 Besides, this study found that the axial elongation (0.11 mm) in the HAL group was marginally lower than that (0.17 mm) for the APOK group, although the difference was not statistically significant. Similarly, a recent study proposed that, the mean axial elongation for the myopic eyes was 0.17 mm for the OK group and 0.10 mm for the HAL group, with no significant difference between the two groups.
46 Furthermore, an annual AL increase in Chinese children aged eight to 11 years typically ranges from 0.16 mm to 0.41 mm.
47 Therefore an annual AL increase of ≤0.15 mm can be considered indicative of minimal myopia progression. Drawing upon the methodology used by Tang et al.,
48 this study analyzed the proportion of individuals with an annual AL increase of ≤0.15 mm. The results revealed that the HAL group had a higher proportion of participants with axial elongation of less than 0.15 mm (59.5%) relative to the APOK (42.9%) and SPOK (25.0%) groups during the one-year follow-up. The synthesis of the available findings indicates that HAL provides the most effective myopia control for children aged eight to 11 years old with low initial myopia, followed by APOK and SPOK lenses.