Objective: To study the dynamic effects of treatment zone decentration on comeal higher-order wavefront aberrations and axial length elongation after orthokeratology. Methods: This prospective study assessed corneal topography and wavefront aberrations before orthokeratology treatment and at l week. 6 months,and l.5 years after overnight orthokeratology lens wear. Axial length elongation was evaluated before and after l.5 years of treatment. Data were analyzed using Pearson correlation, repeated measurements ANOVA and paired t tests. Results: Decentration was located mainly in the inferior temporal quadrant.
The magnitudes of decentration at l week, 6 months, and l.5 years after orthokeratology were located principally within 0.5-1.0 mm. There were no significant differences in the decentration magnitudes at the different follow-up visits after orthokeratology. The root mean squares (RMS) of the total corneal higher-order aberration, third-order aberration, and coma-like aberration were significantly increased by orthokeratology at l week, 6 months, and l.5 years (F=4.491, 5.297. 2.927, P<0.05). Changes of aberrations were not correlated with the decentration at l.5 years after orthokeratology. Axial length elongation was mcreased significantly at l.5 years after orthokeratology (t=-0.725, P<0.05), but there was no significant correlation with the decentration. Conclusions: Decentration of the treatment zone became stable l week after orthokeratology, and it increased the corneal higher-order aberrations at an early stage.However. orthokeratology-induced decentration had no effect on axial length elongation up t0 1.5 years.