comparison of corneal biomechanical characteristics after surface ablation refractive surgery and novel lamellar refractive surgery purpose to investigate and compare corneal biomechanical changes in the form of corneal hysteresis ch and corneal resistance factor crf after smallincision lenticule extraction smile and laserassisted subepithelial keratectomy lasekmethods in this retrospective observational study patients who underwent either smile 36 eyes 21 patients or lasek 35 eyes 19 patients were included data were collected preoperatively and at 1 and 3 months postoperatively which included corneal topography and ocular response analyzer values of ch crf and intraocular pressure iop differences between both surgical groups and the relationships between variables were evaluatedresults ch crf goldmann iop and corneal compensated iop after surgery were significantly lower than the preoperative values p 005 in both surgical groups lenticule thickness lt correlated with crf postoperative preoperative value in the smile group r 0513 p 0001 but the ablation depth ad and crf showed no correlation in the lasek group r 0297 p 0083 in the smile group crflt 0036 001 and chlt 0021 001 values were significantly lower than crfad 0048 002 and chad 0026 002 values in the lasek group p 005conclusions both smile and lasek alter corneal biomechanical strength however the changes induced by smile are more predictable than those induced by lasek in terms of per unit tissue removed smile seems to have less effect on corneal biomechanics than lasek which may be due to preservation of the stiffer anterior stroma