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X. Pan, J. Liu, C. Roberts, S. Shah, M. Laiquzzaman, S. Mantry, I. Cunliffe; Comparing LASIK and LASEK: Indications of Biomechanical Response . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2728.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The effect of LASIK and LASEK procedures on intraocular pressure measurements, as well as the biomechanical properties of corneas is not well understood. In this study, a statistical model was built to analyze the difference in the reduction of measured intraocular pressure (mIOP) and corneal hysteresis, due to two different surgical procedures: LASIK and LASEK. Methods:The best General Linear Models were selected based upon the data collected from 40 surgical eyes at the Midland Eye Institute in UK, analyzed retrospectively. Ten males and 12 females had LASIK procedure, while 7 males and 11 females had LASEK. The effects of surgical procedures on the changes in mIOP and corneal hysteresis, both measured by the Ocular Response Analyzer (ORA, Reichart), were estimated. The influence of gender, age, change in central corneal thickness (ΔCCT), initial corneal hysteresis (ICH), initial central corneal thickness (CCT) and mIOP were investigated. Results: Procedure (LASEK or LASIK), gender, ΔCCT, initial ICH and mIOP were significant predictors of the change in corneal hysteresis, while age and initial CCT were not very influential when other factors were considered already. Procedure (LASEK or LASIK) and initial mIOP were the only two factors that significantly influenced the change in mIOP. Both LASIK and LASEK procedures reduced the mIOP and hysteresis measurement. The reduction of mIOP and hysteresis due to LASEK procedure was significantly greater than that due to LASIK. For mIOP, the difference in reduction between two procedures was 3.14 ± 1.40 mmHg (95% Confidence Interval); and for hysteresis, it was 1.69 ± 0.66 mmHg. The residual variance of the reduction in mIOP due to LASEK was statistically lower than that due to LASIK (P–value < 0.02), while the residual variances of the reduction in measured hysteresis were similar for both procedures. Conclusions: The difference in response between LASIK and LASEK, in terms of both corneal hysteresis and measured IOP, suggests one of two things. Either the biomechanical response of the two procedures is distinct, or the corneas in the two populations were biomechanically distinct prior to surgery.
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