Influence of overnight orthokeratology lens fitting decentration on corneal topography reshaping

Background This retrospective study was designed to investigate the sole influence of orthokeratology (OK) lens fitting decentration on the Zernike coefficients of the reshaped anterior corneal surface. Methods This study comprised a review of 106 right eyes and measurements of corneal topography both before OK and at 1-month follow-up visit. A routine was designed to calculate local corneal surface astigmatism and assist the determination of OK lens fitting decentration from pupil center. The pupil-centered corneal Zernike coefficients of baseline (PCCB) and post-treatment (PCCP) were calculated. Meanwhile, the OK-lens-centered corneal Zernike coefficients of post-treatment (OCCP) were also calculated and considered as the presumptive ideal fitting group without decentration. Relationships between lens fitting decentration and the change of Zernike coefficients including (PCCP − PCCB) and (PCCP − OCCP) were analyzed. Results Patients with a mean age of 11 ± 2.36 years old had an average spherical equivalent refractive error of −3.52 ± 1.06 D before OK. One month after treatment, OK lens fitting decentration from pupil center was 0.68 ± 0.35 mm. RMS of 3rd-order ( P < 0.05), RMS of 4th-order ( P < 0.001) and RMS of total high order ( P < 0.001) corneal Zernike coefficients were increased in PCCP by comparing with OCCP, which was solely caused by lens fitting decentration. Nevertheless, no significant difference was observed in C_2^0 ( P > 0.05). For the high order corneal Zernike coefficients in (PCCP – OCCP), radial distance of decentration was correlated with C_3^-1 ( r = −0.296, P < 0.05), C_3^1 ( r = −0.396, P < 0.001), and C_4^0 ( r = 0.449, P < 0.001), horizontal decentration was significantly correlated with C_3^1 ( r = 0.901, P < 0.001) and C_5^1 ( r = 0.340, P < 0.001), and vertical decentration was significantly correlated with C_3^-1 ( r = 0.904, P < 0.001). Conclusions OK lens fitting decentration within 1.5 mm hardly influenced the change of corneal spherical power for myopia correction, but significantly induced additional corneal high order Zernike coefficients including C_3^-1 , C_3^1 , C_4^0 , and C_5^1 .