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Tariq A. Alhamad, Andrew J. Quantock, Keith M. Meek; Comparison Of Factors That Influence The Measurement Of Corneal Hysteresis In Vitro And In Normal/post-lasik Patients. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5184.
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The purpose of this study was to compare measurements of corneal hysteresis (CH) obtained in vivo, with similar measurements from enucleated human eyes and to determine the other factors that influence the corneal biomechanical properties in normal and post-LASIK patients.
CH was measured using an Ocular Response Analyser from three groups: 53 normal patients, 26 post-LASIK patients and 6 enucleated human eyes. The anterior/posterior corneal curvature and central/peripheral corneal thickness for these patients was measured using the Pentacam.
In vivo, it was found that CH has a weak but significant inverse relationship with IOP both in normal and post-LASIK patients. An identical relationship with IOP was recorded in enucleated eyes, with no significant differences between the behaviour each individual eye. The mean corneal hysteresis values for normal patients (10.76 ± 0.71mmHg) were higher than those of post-LASIK patients (8.89± 0.44 mmHg). There was no significant change in posterior corneal curvature between normal and post-LASIK groups (6.47± 0.12mm and 6.56 ± 0.23 mm respectively) nor was there a significant correlation between CH and either anterior or posterior corneal curvature. However, a significant correlation was found between CH and central/peripheral corneal thickness in normal and post-LASIK patients. The mean central corneal thickness in normal and post-LASIK respectively was 550.92 ± 25.56µm and 437.76 ± 25.23µm. The mean peripheral corneal thickness (3mm from centre) was 648.65 ± 31.14µm in normal and 595.15 ± 37.92µm post-LASIK.
The results indicate that every normal enucleated human eye shows the same dependence of CH on IOP and that this relationship is a therefore an intrinsic property of the organ, and does not change post-mortem. We confirm that LASIK decreases CH but also that posterior curvature is unchanged. We have shown that CH depends on IOP, central/peripheral corneal thickness but is independent of anterior and posterior corneal curvature.
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