Clinical Study of Corneal Asphericity and Visual Quality after Q-Factor-Guided and Standard FS-LASIK

Objective: To compare the differences in corneal asphericity and contrast sensitivity under different conditions before and after Q-value-guided femtosecond laser in situ keratomileusis (FS-LASIK) and standard FS-LASIK for myopia, and evaluation of the efficacy of the two surgical methods for treating myopia. Methods: This was a prospective cohort study. A total of 64 moderate and low myopia patients (33 patients, 64 eyes, in the Q-guided group and 31 patients, 62 eyes, in the standard group) who were treated by FS-LASIK were selected from Laser Center, the First Affiliated Hospital of Anhui Medical University, during the same period. Visual acuity, Q-value, corneal aberration and contrast sensitivity were measured and compared before and after surgery. All the cases were followed up at 1 and 3 months. A repeated measures analysis of variance, t-test and rank sum test were used for data analysis. Results: There was no statistically significant difference for the data before surgery. The uncorrected visual acuity (UCVA) and residual refractive error of all eyes were not significantly different between the two groups after 3 months of follow-up. In the corneal 6 mm range, there was no significant difference in Q-value, spherical aberration or coma between the two groups at 3 months postoperatively. In the corneal 4.5 mm range, the Q-values and spherical aberrations of the Q-value-guided group were significantly less than that for the standard LASIK group (tSA=2.00, P=0.04; tQ=2.28, P=0.03). After surgery, contrast sensitivity in the two groups returned to preoperative levels at different spatial frequencies in various environments, and it tended to be stable at 3 months after surgery. At 3 months after surgery, the visual quality of the Q-value-guided group was better than that of the standard group under mesopic circumstances with glare (Z3 c/d=-2.0, P=0.044; Z6 c/d=-2.1, P=0.034). Conclusions: Q-value-guided LASIK for myopia and astigmatism is as safe and effective as standard FS-LASIK. Further more, Q-value-guided LASIK results in better visual quality than standard FS-LASIK under mesopic circumstances with glare. Key words: laser in situ keratomileusis; femtosecond laser; wavefront aberration; visual quality