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T. Gaujoux, Sr., J. C. Gavrilov, M. Sellam, R. Kopito, M. A. Chatel, O. Touzeau, B. Ameline, V. M. Borderie, L. Laroche; Changes in Corneal Biomechanics Following Corneal Refractive Surgery: LASIK versus PRK. Invest. Ophthalmol. Vis. Sci. 2008;49(13):650.
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© ARVO (1962-2015); The Authors (2016-present)
To analyse pre- and postoperative measurements of corneal biomechanical properties using the Reichert ocular response analyzer (ORA) in myopic eyes undergoing LASIK or PRK.
A total of 37 eyes of 22 patients were involved in the study. LASIK was performed in 26 eyes and PRK in 11.Corneal hysteresis (CH) and corneal resistance factor (CRF) were recorded with the Reichert ORA prior to and 1 month after surgery.Other clinical parameters including preoperative central corneal thickness (CCT), preoperative spherical equivalent and theoretic stromal ablation depth were also recorded.Correlations between clinical parameters were obtained.
Mean preoperative spherical equivalent was - 4.2 +/- 1.4 D (ranging -2 to -7.25).Before surgery, the mean CH value was 10.3 +/- 1.1 mm Hg and the mean CRF: 10.2 +/- 1.0 mm Hg. There was no difference between the LASIK and PRK groups for CH and CRF (p = 0.43 and 0.24 respectively).The preoperative CH value was correlated with preoperative spherical equivalent (rs = - 0.43; p = 0.005) and with preoperative CCT (rs = 0.59; p < 0.001).Mean CH showed a statistically significant decrease following LASIK and PRK in all eyes (p<0.01).Postoperatively, CH decreased from 10.3 to 8.3 mm Hg (19.6 %), CRF from 10.3 to 7.3 mm Hg (29.8 %) in the LASIK group and CH decreased from 10.4 to 7.9 mm Hg (24.1 %), CRF from 10.0 to 7.0 mm Hg (30.8 %) in the PRK group.Reduction of biomechanical parameters were no statistically different between post-LASIK eyes and post-PRK eyes (p = 0.10 and 0.46 for CH and CRF respectively).Decrease of CH and CRF was correlated with theoretic stromal ablation depth (rs = 0.55; p < 0.001 for CH and rs = 0.75; p < 0.001 for CRF).
Corneal hysteresis decreased following LASIK and PRK which may reflect respective changes in the viscous and elastic qualities of the cornea after corneal refractive surgery.Similar reductions occurred following both procedures, indicating that LASIK involving a thin 160 µm flap did not induce additional biomechanical change. Future work is needed to confirm these results.
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