Changes in corneal biomechanics during small-incision lenticule extraction (SMILE) and femtosecond-assisted laser in situ keratomileusis (FS-LASIK)

Observe the influence of femtosecond laser cutting on corneal biomechanics during small-incision lenticule extraction (SMILE) or femtosecond-assisted laser in situ keratomileusis (FS-LASIK) and assess the biomechanical changes following the operation. Prospective, non-randomized study. A total of 80 eyes from 80 patients were treated with either SMILE or FS-LASIK. Parameters of inverse concave radius, deformation amplitude ratio 2 mm or 1 mm (DA ratio 2 mm or 1 mm), highest concavity radius (HC radius), biomechanically corrected intraocular pressure (bIOP), and central corneal thickness (CCT) measured by Corvis ST II were recorded at 1 day preoperatively, immediately after the lenticule or flap creation, during subsequent lenticule extraction or excimer laser ablation, and during follow-up at 1 week, 1 month and 3 months postoperatively. After lenticule creation, the DA ratio 2 mm or 1 mm was bigger (p 0.05) after operation. The variations in bIOP (ΔbIOP) after operation were significantly less than those in Δnon-contact IOP (p < 0.001) in two groups. Femtosecond laser cutting during lenticule creation has a greater impact on corneal biomechanics than flap creation. Both the femtosecond laser cutting and removal of tissue degrade corneal biomechanics; however, these effects may be predominantly a result of tissue removal. SMILE and FS-LASIK have no differences in corneal biomechanics when the same CCT is consumed. bIOP is more reliable after the operation, but further study is essential.