Background/Objectives: To examine the trend of treatment zone (TZ) decentration over 12 months of Orthokeratology (OK) wear using two corneal refractive therapy (CRT) lens designs: standard (STD) and dual axis (DA). Methods: A prospective, randomized, longitudinal study was conducted at the Optometry Clinic of the Complutense University of Madrid. Subjects were fitted with STD or DA designs in one of the eyes, randomly. Refraction, uncorrected visual acuity (VA) and corneal topography were performed at baseline, 1-night, 1-week, 1-, 3-, 6- and 12-month of lens wear. Subjects requiring lens parameter adjustments or replacements after 3 months were excluded. Decentration was measured by subtracting pre-OK from post-OK tangential curvature maps at each visit, with decentration distance and corneal optical TZ measured using MATLAB. Correlations between decentration and visual acuity (VA) were also analyzed.

Inclusion Criteria:

• Age between 8 to 17 years old
• Myopia up -6.00 D

Exclusion Criteria:

• Ocular diseases