Comparison of Visual Outcomes for Myopia after Refractive Surgery using Femtosecond Laser-assisted and Epipolis LASIK

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Purpose This study was to clinically evaluate the visual outcomes after refractive surgery for myopia using femtosecond laser-assisted in situ keratomileusis (femto-LASIK) and epipolis LASIK (flap-off epi-LASIK). Methods Forty eyes of 27 patients were divided into 2 groups in a retrospective study. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction (MR),corneal asphericity (Q-value) and corneal higher-order aberrations (HOAs) were assessed pre- and postoperatively. Results The pre- and postoperative changes in flattest keratometry reading(K1), steepest keratometry reading(K2), central corneal thickness(CCT), and only Q-value of the anterior surface was statistically significant for both groups (femto-LASIK: P=0.014, P=0.03, P<0.001, P=0.001, respectively; epi-LASIK: all P<0.001). The postoperative corneal thickness spatial profile (CTSP) were statistically significant thinner than preoperative CTSP in both procedures (all P<0.05), and the epi-LASIK was significant thinner than femto-LASIK at 6 mm ring of CTSP (P=0.039). The improvement in LogMAR UDVA after refractive surgery was statistically significant for both groups (P<0.001 for all groups); it was significantly improved for femto-LASIK on day 1 and at 1 week postoperatively (P<0.001, P=0.019, respectively). In analysis of corneal HOAs, there were significant reduction of vertical coma aberration and horizontal secondary astigmatism aberration, and induction of spherical aberration in the front corneal HOAs after femto-LASIK (P=0.021, P=0.001, P=0.001, respectively); in the total corneal HOAs changes were the same pattern as the front corneal HOAs (P=0.007, P=0.004, P<0.001, respectively), but in the back corneal HOAs changes, a few significant induction of vertical coma aberration, and reduction of oblique trefoil aberration and oblique tetrafoil aberration (all P<0.05). In flap-off epi-LASIK, there were only significant induction of SA in the front and total corneal HOAs after surgery (all P<0.05); in the back corneal HOAs, a few significant induced horizontal secondary astigmatism aberration and reduced SA aberration (P=0.027, P=0.011, respectively), however, the back corneal HOAs changes were not significant effect on the total corneal HOAs changes. Conclusion Femto-LASIK showed better early visual outcomes than that noted by epi-LASIK, but there was no significant difference between the outcomes of the 2 procedures 1 week postoperatively.