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X. Pan, C.J. Roberts, S. Shah, M. Laiquzzaman, S. Mantry, I. Cunliffe; Comparing LASIK and LASEK . Invest. Ophthalmol. Vis. Sci. 2006;47(13):559.
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To compare the effect of LASIK and LASEK procedures on intraocular pressure measurements, as well as the biomechanical properties of the cornea.
Eighty eyes of forty one subjects treated at the Midland Eye Institute were enrolled in this retrospective study, divided into three groups of patients: LASEK for Myopia (group1), LASIK for Myopia (group2) and LASIK for Hyperopia (group3). The pre–op to 3 months post–op changes of four measurements produced by the Reichert Ocular Response Analyzer (ORA) were studied: Goldman correlated intraocular pressure (IOPg), corneal compensated IOP (IOPcc), corneal hysteresis (CH), and corneal resistance factor (CRF). The best General Linear Models were selected based upon these data. The effects of surgical procedures and myopia/ hyperopia on the changes in IOPg, CH, IOPcc and CRF were estimated. The influence of gender, age, change in central corneal thickness (ΔCCT), initial corneal hysteresis (ICH), initial central corneal thickness (ICCT), and initial IOPg and IOPcc were investigated.
Group3 patients (hyperopia) had statistically significant less change than group1 and group2 patients (Myopia) for all four measurements. For myopia patients, both LASIK and LASEK procedures reduced IOPg, hysteresis and CRF while increased IOPcc. The changes of all four measurements were not significantly different between the LASEK and LASIK for myopia patients. The changes of these four measurements were dependent on the patient’s initial conditions and gender.
The myopia patients had a distinct measured IOP response from the hyperopia patients, which cannot be explained by the difference in thickness change, and is therefore due to a difference in the modification of biomechanical properties, as evidenced by CH and CRF. No statistical differences were observed between LASIK and LASEK three months after surgery, in terms of changes in IOPg, CH, IOPcc and CRF. Previous studies reported differences between the two surgical procedures were found in a long term analysis . Our study suggests that the three month period was not sufficient to observe the difference in biomechanical response between the two procedures. Therefore, further follow up on these patients is planned.  Hjortdal J et. al.. Journal of Cataract and Refractive Surgery, 31 (1): 21–29, 2005
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