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J. Pepose, M.A. Qazi, C.J. Roberts; Relationship Between Corneal Hysteresis, Intraocular Pressure, and Flap Dimensions in LASIK Patients . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4853.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To compare the preoperative and postoperative measurements of intraocular pressure (IOP) using the Reichert Ocular Response Analyzer (ORA) and Goldmann applanator, and to correlate measurements of corneal viscoelasticity to flap dimensions from microkeratome–assisted laser in situ keratomileusis. Methods: Patients scheduled for LASIK underwent standard preoperative testing, including ultrasound pachymetry and slit–scanning videokeratography. Preoperatively, intraocular pressure was measured using the ORA and Goldmann applanation techniques. ORA parameters of IOP and corneal hysteresis were recorded. Intraoperatively, flap ultrasound pachymetry and flap diameter were recorded. Measurements for IOP, pachymetry, and videokeratography were repeated at the first postoperative week. Statistical analysis was performed to evaluate postoperative changes in IOP measurement using these techniques. Results: For corneas with a mean decrease in postoperative pachymetry by 95.4 + 26.1 µm, there was a reduction in post–LASIK IOP measurements using both ORA (by –1.8 + 0.7 mm Hg) and GAT (by –2.8 + 4.8 mm Hg). Corneal hysteresis decreased by –1.30 + 0.89 mm Hg following LASIK (p=.02). LASIK–induced alteration of corneal hysteresis correlated more closely to changes in ORA IOP than changes in GAT. Conclusions: The corneal hysteresis feature of the ORA can be used to better interpret post–LASIK IOP. Correlation of corneal hysteresis to flap dimension can assist in the understanding of corneal biomechanics during LASIK. Comparisons to pre– and postoperative IOP measurements with the PASCAL Dynamic Contour Tonometer (Zeimer Ophthalmic Systems) will also be presented.
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