The effect of orthokeratology lens optical zone size on myopia control in adolescents

Background This study aims to investigate the impact of different optical zone sizes in orthokeratology (Ortho-K) lenses on myopia control in adolescents. Methods A retrospective study was conducted on 84 subjects who had undergone Ortho-K lens treatment for over 12 months. Subjects were divided into two groups based on the optical zone size: 5-mm and 6-mm. The study compared changes in axial length, corneal curvature, corneal astigmatism, nasal defocus (ΔN), temporal defocus (ΔT), and the diameter of the peripheral plus power ring (PPRD). Additionally, corneal safety indicators, including corneal staining rate, corneal endothelial cell density, and visual acuity, were evaluated. Results Data from the right eyes of 43 patients in the 5-mm group and 41 patients in the 6-mm group were analyzed. Baseline axial lengths were 24.77 ± 0.64 mm and 24.87 ± 0.75 mm, respectively. After 12 months of Ortho-K lens wear, the mean change in axial length was 0.25 ± 0.17 mm in the 5-mm group and 0.29 ± 0.16 mm in the 6-mm group, Repeated measures ANOVA revealed a significant time effect ( F = 48.634, P < 0.001), a significant group effect ( F = 4.041, P = 0.048), and a non-significant interaction effect between time and group ( F = 2.361, P = 0.101). Multivariate linear regression analysis showed that age was negatively correlated with axial elongation (β = −0.557, 95% CI: −0.067 to −0.036, P < 0.001), while PPRD was positively correlated (β = 0.332, 95% CI: 0.055–0.163, P < 0.001). No significant differences were observed in safety indicators, including corneal staining rate, corneal endothelial cell density, and visual acuity. Conclusion For adolescents with low-to-moderate astigmatism, 5-mm Back Optical Zone Diameter (BOZD) Ortho-K lenses demonstrated slightly superior efficacy in controlling myopia progression compared to 6- mm lenses, characterized by a smaller PPRD and higher defocus quantity. Measuring PPRD 1 month after lens wear may predict future axial length control.