Changes in Ocular Response Analyzer Parameters After LASIK

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 post-operatively (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 Delta CRF (r=0.457) than for Delta CH (r=0.271). Delta CH was negatively correlated to flap thickness (r=-0.361) and the ratio of flap thickness to preoperative central corneal thickness (r=-0.442) whereas Delta CRF was not. Delta CH was positively correlated with Delta IOPcc, and Delta CRF was positively correlated with Delta IOPg. Delta IOPg was positively correlated with Delta CCT whereas Delta IOPcc was riot. 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. [J Refract Surg. 2010;26:279-288.] doi:10.3928/1081597X-20100218-04