Is Orthokeratology Treatment Zone Decentration Effective and Safe in Controlling Myopic Progression?

Objective: To compare the myopia control efficacy and safety of decentered versus centered positioning of orthokeratology. Methods: This is a retrospective intrasubject study, including 46 children with myopia (25 boys, 21 girls; age 11.12 +/- 0.33 years) treated for 1 year with OK decentration in one eye (group D) and central location in the other (Group C). Axial length was measured before and at 6 months and 12 months after the initial lens wear, respectively. Corneal topography was measured at baseline and at 1-month after lens wear. The corneal topography obtained from the 1-month visit was used to quantify treatment zone decentration (TZD) for each subject. Cycloplegic refraction was required for all children before fitting the orthokeratology lenses. Results: No differences were found between the groups in the biological ocular parameters (P >= 0.05 for all). The axial elongation in group D and group C differed after 6 and 12 months (P<0.001 for all). Similar corneal staining rates (P=0.06) were noted during follow-up in groups D (n=20; 7.24%) and C (n=10; 3.62%), all of grade I. The uncorrected visual acuity (UCVA) in group D and C differed after 1, 6, and 12 months (P=0.002, 0.010, 0.044), except 3 months (P=0.146). Group D (n=32; 17.39%) was more likely to have glare or ghosting (chi-squared test, P<0.001) than group C (n=12; 6.52%) during follow-up visits. Axial elongation was significantly associated with baseline spherical equivalent (SE) in group C (P=0.019). In group D, axial elongation was significantly associated with SE and TZD (P<0.05 for all). Conclusions: This intrasubject study showed that when the UCVA was acceptable and there were no apparent complications, orthokeratology decentration may be beneficial in controlling the progression of myopia. Axial elongation became slower in children with a higher SE and a larger TZD, because TZD ranged from 0.5 mm to 1.5 mm.