Changes in corneal biomechanics and intraocular pressure following Femto-LASIK using Goldman applanation tonometry and ocular response analyzer.

Abstract

To compare intraocular pressure (IOP) measurements before and after laser in situ keratomileusis (LASIK) with a femtosecond laser for flap creation using ocular response analyzer (ORA) and Goldmann applanation tonometry, and to identify factors that may influence the preoperative and postoperative IOP. A prospective study conducted on myopic patients who underwent LASIK using a femtosecond laser for flap fashioning. Enrolled patients were evaluated preoperatively, 6wk and 3mo postoperatively for manifest refraction (MR), keratometric (K) readings and central corneal thickness (CCT) using a scheimpflug-based topography. Corneal resistance factor (CRF), corneal hysteresis (CH), Goldmann correlated IOP (IOPg) and corneal compensated IOP (IOPcc) were measured using ORA besides IOP assessment by Goldman applanation tonometry (GAT). There was a statistically significant decrease in measures of IOPg by 3.35±0.83 mm Hg, followed by GAT which decreased by 2.2±0.44 mm Hg, and the least affected by operation was IOPcc which decreased only by 0.87±0.1 mm Hg after 6wk. After 3mo follow up there was a statistically significant decrease in IOPcc which decreased only by 0.76±0.4 mm Hg, followed by IOP GAT by 1.6±0.5 mm Hg, and the most affected by operation was IOPg which decreased by 2.3±0.3 mm Hg. Correspondingly, there was a statistically significant decrease in CH and CRF after 6wk and 3mo. At 3mo, the preoperative MR and preoperative GAT were prominent significant predictors of the postoperative GAT changes. The prediction equation was subsumed. IOP measurements and corneal biomechanical factors reduce significantly after LASIK with a femtosecond laser for flap creation. The IOPcc values are less influenced by changes in corneal properties than IOPg and GAT, indicating that IOPcc may provide the most reliable measurement of IOP after this procedure.