Long-term higher-order aberration study on Q-value optimized aspheric ablation in high myopia

Abstract

Objective To observe the long-term changes in Q-value and higher-order aberrations after Q-value optimized ablation in high myopia.Methods Seventy eyes of 35 high myopic patients treated with Q-value optimized ablation were retrospectively studied,including 34 eyes of 17 patients treated with laser in situ keratomileusis (LASIK) and 36 eyes of 18 patients treated with laser epithelial keratomileusis (LASEK).Preoperative and long-term postoperative Q-value and higher-order aberrations were compared using a paired t test and an independent samples t test and the differences and influential factors were analyzed using Pearson correlation and linear regression.Results All patients had visual acuity over 0.8.Both Q-value optimized LASIK and LASEK had greater safety than one and validity close to one.Compared to preoperative Q-value,postoperative Q-value in both the LASIK and LASEK groups had changed from negative to positive.The differences in higher-order aberrations between preoperative and postoperative data were statistically significant in both groups (t=-3.90,-6.75,P＜0.01).Root mean square (RMS) value of third order (t=-3.50,-5.22),RMS value of fourth order (t=-6.79,-10.14),RMS value of spherical aberration (t=-8.57,-13.79) and RMS value of vertical coma (t=5.73,-5.50) in both groups showed statistically significant increases during the 3 years after surgery (P＜0.01).The changes in RMS value of vertical coma and RMS value of spherical aberration were not statistically different between the two groups.The horizontal coma had no significant change postoperatively.Postoperative higher-order aberrations (R2=0.372,F=16.96,P＜0.01) and spherical aberration (R2=0.2.24,F=10.93,P＜0.01 ) were correlated to preoperative spherical equivalent and optic zone.Postoperative vertical coma was correlated to preoperative spherical equivalent and target Q-value (R2=0.224,F=10.93,P＜0.01).Conclusion In high myopia,Q-value optimized ablation had good safety,efficacy and good predictability.Over 3 years,higher-order aberrations and spherical aberration increased while vertical coma decreased with no difference between two surgeries.Increase of the vertical coma may be relevant to the direction of flap hinge.Higher-order aberrations after surgery were mainly correlated to preoperative spherical equivalent and optic zone size. Key words: Myopia,degenerative; Q-value; Aspheric ablation; High-order aberrations; Keratomileusis,laser in situ; Keratectomy,subepithelial,laser-assisted