Abstract
PurposeTo investigate the predictive factors of postoperative myopic regression among subjects who have undergone laser-assisted subepithelial keratomileusis (LASEK), laser-assisted in situ keratomileusis (LASIK) flap created with a mechanical microkeratome (MM), and LASIK flap created with a femtosecond laser (FS). All recruited patients had a manifest spherical equivalence (SE) from − 6.0D to − 10.0D myopia.MethodsThis retrospective, observational case series study analyzed outcomes of refraction at 1 day, 1 week, and 1, 3, 6, and 12 months postoperatively. Predictors affecting myopic regression and other covariates were estimated with the Cox proportional hazards model for the three types of surgeries.ResultsThe study enrolled 496 eyes in the LASEK group, 1054 eyes in the FS-LASIK group, and 910 eyes in the MM-LASIK group. At 12 months, from − 6.0D to − 10.0D myopia showed that the survival rates (no myopic regression) were 52.19%, 59.12%, and 58.79% in the MM-LASIK, FS-LASIK, and LASEK groups, respectively. Risk factors for myopic regression included thicker postoperative central corneal thickness (P ≦ 0.01), older age (P ≦ 0.01), aspherical ablation (P = 0.02), and larger transitional zone (TZ) (P = 0.03). Steeper corneal curvature (Kmax) (P = 0.01), thicker preoperative central corneal thickness (P < 0.01), smaller preoperative myopia (P < 0.01), longer duration of myopia (P = 0.02), with contact lens (P < 0.01), and larger optical zone (OZ) (P = 0.02) were protective factors. Among the three groups, the MM-LASIK had the highest risk of postoperative myopic regression (P < 0.01).ConclusionsThe MM-LASIK group experienced the highest myopic regression, followed by the FS-LASIK and LASEK groups. Older age, aspheric ablation used, thicker postoperative central corneal thickness, and enlarging TZ contribute to myopic regression; steeper preoperative corneal curvature (Kmax), longer duration of myopia, with contact lens, thicker preoperative central corneal thickness, lower manifest refraction SE, and enlarging OZ prevent postoperative myopic regression in myopia from − 6.0D to − 10.0D.
Highlights
Postoperative refractive stability has been a concern since excimer corneal refractive surgery was first introduced more than 30 years ago
The MM-laser-assisted in situ keratomileusis (LASIK) had the highest risk of postoperative myopic regression (P \ 0.01)
Previous studies have primarily shown the clinical outcomes of single surgery, laser-assisted in situ keratomileusis flap created with a femtosecond laser (FS-LASIK) or laser-assisted in situ keratomileusis flap created with a mechanical microkeratome (MMLASIK) [5, 8]
Summary
Postoperative refractive stability has been a concern since excimer corneal refractive surgery was first introduced more than 30 years ago. Various regression associated factors included corneal thickness [1], age [2, 7], intraocular pressure (IOP) [8], flap thickness [9], optical zone (OZ) diameter, and thin preoperative corneal thickness of high myopia [4]. Previous studies have primarily shown the clinical outcomes of single surgery, laser-assisted in situ keratomileusis flap created with a femtosecond laser (FS-LASIK) or laser-assisted in situ keratomileusis flap created with a mechanical microkeratome (MMLASIK) [5, 8]. Most published studies applied a simple descriptive analysis, without adjustment for other factors that could affect myopic regression
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