Long-term Effect of Orthokeratology Lenses on Axial Length Elongation in Myopia: 2-3 Years Follow-up Study

Purpose: To evaluate the effect of orthokeratology lenses on axial length elongation and associated factors in eyes treated with orthokeratology lenses for 2-3 years. Methods: Thirty-four eyes of 20 patients treated with orthokeratology lenses for more than 22 months were enrolled into the orthokeratology (OK) group. Uncorrected distant visual acuity, spherical equivalent, axial length, and high-order aberrations of the anterior cornea at baseline and during the follow-up period were analyzed retrospectively. Spectacle-wearing patients matched with the OK group patients by sex, age, refractive error and follow-up period were selected as a control group. To adjust for follow-up period differences, the 24-month conversion axial length changes were calculated and compared between the two groups. Results: The 24-month conversion mean axial length change showed significant differences (0.50 +/- 0.23 mm in the OK group versus 1.00 +/- 0.28 mm in the control group; p < 0.001). For the OK group, the age at starting OK lens (r = -0.572, p = 0.001) showed statistically significant correlation with axial elongation. The anterior corneal spherical aberrations (SA) and coma with 6 mm pupil at last follow-up (SA: r = 0.543, p = 0.001; coma: r = 0.420, p = 0.017) and the total SA and total coma changes (Delta SA: r = 0.518, p = 0.002; Delta coma: r = 0.420, p = 0.017) also showed a statistically significant correlation. The initial age and axial length, the anterior corneal SA and A SA values were identified as factors significantly correlated with axial length elongation by multiple regression analysis. Conclusions: The OK lens effectively suppressed axial length elongation during a 2-3 years treatment period. However, when the age of starting OK lens was younger and the anterior corneal spherical aberration during the follow-up period was larger, the risk of axial elongation was higher.