Cont Lens Anterior Eye . 2026 Mar 9;49(3):102632. doi: 10.1016/j.clae.2026.102632. Online ahead of print. ABSTRACT PURPOSE: To analyze the effect of minor reducing the back optical zone diameter (BOZD) of orthokeratology (OK) lenses on myopia control in Chinese children. METHODS…
Cont Lens Anterior Eye. 2026 Mar 9;49(3):102632. doi: 10.1016/j.clae.2026.102632. Online ahead of print.
ABSTRACT
PURPOSE: To analyze the effect of minor reducing the back optical zone diameter (BOZD) of orthokeratology (OK) lenses on myopia control in Chinese children.
METHODS: This retrospective study recruited 35 myopic children corrected with conventional OK lenses who switched to a smaller BOZD design (ΔBOZD ≥ 0.4 mm). Corneal treatment zone area (TZA), decentration, maximum relative corneal refractive power (RCRPmax) and its distance from the pupil center (Xmax) were calculated from the tangential difference map using MATLAB. The 12-month axial elongations (AE) before and after switching were assessed and compared with that of children continuing conventional BOZD lenses over the same two-year period. Associations between the changes in AE changes and these topographic parameters before and after treatment with smaller BOZD lenses were analyzed.
RESULTS: Smaller BOZD lenses significantly reduced 12-month AE by 0.08 mm in the second year versus unchanged BOZD (F = 5.58, P = 0.02). In the BOZD-altered group, smaller BOZD lenses (5.68 ± 0.12 mm vs. 6.17 ± 0.07 mm) retarded myopia progression (0.26 ± 0.11 mm vs. 0.16 ± 0.12 mm, t = 4.24, p < 0.001) and yielded a smaller corneal treatment zone (8.69 ± 1.91 mm2 vs. 7.42 ± 1.30 mm2, t = 4.41, p < 0.001). No significant differences were observed in decentration (0.47 ± 0.23 mm vs. 0.48 ± 0.22 mm, t = -0.16, p = 0.88), RCRPmax (11.71 ± 6.27 D vs. 12.05 ± 5.38 D, t = -0.36, p = 0.72), or Xmax (2.54 ± 0.61 mm vs. 2.38 ± 0.60 mm, t = 1.02, p = 0.31) between different BOZD lenses treatments. When switching to smaller BOZD lenses, the change in 12-month AE was negatively correlated with the change in Xmax (β = - 0.059, P = 0.032) but not with other topographic parameters (all p > 0.05).
CONCLUSION: Reducing the BOZD of OK lenses by approximately 0.5 mm from the conventional design slowed second-year axial elongation by more than one-third and minimally affected visual acuity (2-letter decrease), without impacting lens centration. This approach may be considered as an initial option for children using OK lenses for myopia control.
PMID:41806505 | DOI:10.1016/j.clae.2026.102632