Regional analysis of posterior corneal elevation after three laser refractive surgeries for correction of myopia of different degrees

Abstract

Abstract Objectives To evaluate the regional changes of posterior corneal elevation after three laser refractive surgeries for correction of myopia of different degrees. Methods 200 patients (200 eyes) who underwent laser epithelial keratoplasty (LASEK), femtosecond-assisted laser in situ keratomileusis (FS-LASIK) and small-incision lenticule extraction (SMILE) were included in this retrospective, comparative and non-randomized study. According to preoperative spherical equivalent (SE), each surgical group was divided into two refractive subgroups with low to moderate myopia (LM group) and high myopia (H group). The posterior corneal elevation from Pentacam Scheimpflug tomography was analyzed preoperatively and 1 month, 3 months, 6months and 12months postoperatively. Three subregions of the posterior cornea were divided in this study as the central, paracentral and peripheral region. Results For all the three surgical groups, similar changing trends were shown in the two refractive subgroups. H group presented larger changing magnitude than LM group in FS-LASIK over time (P < 0.05), whereas no significant difference was noted in the two refractive subgroups of LASEK or SMILE (P > 0.05). At 12 months postoperatively, the central posterior corneal elevation returned to the preoperative level in LASEK (P > 0.05), but shifted forward significantly in FS-LASIK and SMILE (P < 0.05). Conclusions Different posterior corneal regions respond differently to corneal refractive surgeries. LASEK, FS-LASIK and SMILE demonstrate different trends in the regional changes of posterior corneal elevation. The corneal shape seems more stable in LASEK than in FS-LASIK and SMILE.