Optical changes and axial elongation in children wearing orthokeratology lenses of smaller back optic zone diameter: a systematic review and meta-analysis

Objectives To evaluate the effect of orthokeratology lenses (Ortho-K) with smaller back optic zone diameters (BOZD) on axial elongation and ocular higher-order aberrations in children and adolescents. Methods PubMed, the Cochrane Library, Embase, CNKI, and Web of Science databases were comprehensively searched for relevant studies. The Cochrane risk-of-bias tool and the Newcastle-Ottawa Scale were used to assess the risk of bias in the included studies. RevMan 5.4 was applied for meta-analysis, and STATA 17.0 was employed for meta-regression, sensitivity analysis, and publication bias assessment. This study was registered at PROSPERO (registration number CRD42024538742). Results Seventeen studies were included, comprising nine RCTs and eight cohort studies, with 1,548 participants in the smaller BOZD group and 1,570 in the conventional BOZD group. Meta-analysis shows that the smaller BOZD group has a lower axial elongation than the conventional BOZD group at 6 months, 12 months, and 24 months following Ortho-K treatment, with reductions of −0.07 mm (95% CI [−0.09, −0.04] P < 0.00001), −0.12 mm (95% CI [−0.13, −0.10] P < 0.00001), and −0.14 mm (95% CI [−0.19, −0.08]; P < 0.00001), respectively. Furthermore, compared to the conventional BOZD group, the smaller BOZD group result in a smaller treatment zone diameter (TZD) (MD: −0.49; 95% CI [−0.62, −0.36] P < 0.00001) and increased root mean square (RMS) higher-order aberrations (MD: 0.20; 95% CI [0.16–0.24]; P < 0.00001), RMS spherical aberration (MD: 0.17; 95% CI [0.12–0.21]; P < 0.00001) and RMS coma (MD = 0.10, 95% CI [0.02–0.18]; P < 0.0001) in children. Conclusions Our meta-analysis revealed that Ortho-K lenses with smaller BOZD exhibited less axial elongation in children compared with conventional Ortho-K lenses. This effect may be related to the reduction of TZD and the increase of higher-order aberrations (HOAs) caused by the smaller BOZD design.