Intraocular pressure changes and corneal biomechanics after hyperopic small-incision lenticule extraction

Background We aimed to compare the intraocular pressure (IOP) measurements by a dynamic Scheimpflug analyzer (Corvis ST), a non-contact tonometer, and an ocular response analyzer after hyperopic small-incision lenticule extraction (SMILE). Methods Thirteen patients who underwent hyperopic SMILE in one eye were enrolled prospectively. IOP and corneal biomechanical parameters were measured preoperatively and at 1 week, 1 month, and 3 months postoperatively with a non-contact tonometer (IOPNCT), Corvis ST (biomechanical corrected IOP [bIOP]), and ocular response analyzer (Goldmann-correlated intraocular pressure [IOPg] and cornea compensated IOP [IOPcc]). A linear mixed model was used to compare the IOPs and biomechanical values among methods at each time point. Results IOPNCT, IOPg, and IOPcc dropped significantly after surgery, with the amplitude being 3.15 +/- 0.48 mmHg, 5.49 +/- 0.94 mmHg, and 4.34 +/- 0.97 mmHg, respectively, at the last follow-up visit. IOPNCT decreased by 0.11 +/- 0.06 mmHg per mu m of excised central corneal thickness. bIOP did not change significantly after surgery. Preoperatively, no difference was found among the four measurements (P > 0.05). Postoperatively, IOPNCT and bIOP were higher than IOPg and IOPcc. bIOP was independent of cornea thickness at last follow-up visit, whereas it correlated significantly with corneal biomechanics similar to the other three IOP values. Conclusion bIOP is a relative accurate measure of IOP after hyperopic SMILE.