Changes in ocular response analyzer parameters after LASIK

Abstract

Purpose: To investigate changes in Ocular Response Analyzer parameters after myopic LASIK.

Methods: Thirty myopic patients (60 eyes) undergoing bilateral LASIK were studied prospectively. Corneal hysteresis, corneal resistance factor, Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated IOP (IOPcc) measurements were obtained with the Ocular Response Analyzer before and after LASIK. Central corneal thickness and corneal flap thickness were also measured with optical coherence tomography.

Results: Compared with preoperative baseline values, corneal hysteresis, corneal resistance factor, IOPg, IOPcc, and central corneal thickness decreased postoperatively (P<.01). Corneal hysteresis (CH), corneal resistance factor (CRF), IOPg, IOPcc, and central corneal thickness (CCT) increased between 10 days and 3 months (post-hoc, P<.05). (The differences between the preoperative values and those at 3 months postoperatively are denoted by Delta.) The correlation of the ablation depth was stronger for DeltaCRF (r=0.457) than for DeltaCH (r=0.271). DeltaCH was negatively correlated to flap thickness (r=-0.361) and the ratio of flap thickness to preoperative central corneal thickness (r=-0.442) whereas DeltaCRF was not. DeltaCH was positively correlated with DeltaIOPcc, and DeltaCRF was positively correlated with DeltaIOPg. DeltaIOPg was positively correlated with DeltaCCT whereas DeltaIOPcc was not.

Conclusions: Corneal biomechanical properties measured by corneal hysteresis and corneal resistance factor were decreased at 10 days after LASIK. Minimal recovery (approximately 10% of the changes) was achieved by 3 months. The changes in biomechanical properties may affect IOP measurement.