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A. Laurenzi, L. Echeverria, J. Ramos-Estanban, R. Krueger; Corneal and Flap Thickness Monitoring With OCT During and Following Intra LASIK. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5339.
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To determine time-dependent changes in corneal thickness (CT) and Flap Thickness (FT) induced by Femtosecond laser flap creation during LASIK using Optical Coherence Tomography (OCT).
Retrospective review of 17 consecutive IntraLASIK eyes (IntraLase, Irvine CA). CT OCT pachymetry maps were obtained before and immediately after flap creation, and one day and one week after surgery. OCT CT and FT were measured at the corneal apex and 1.5 and 3.0 mm left from the center of the apex. Differences in CT and FT measurements were tested for significance using paired t-test at the different study time points.
11 myopic eyes (mean spherical equivalent -3.88D ± 1.68) and 6 hyperopic eyes (mean spherical equivalent +2.59D ± 2.66) were included. Mean OCT CT central values were preoperatively 538.35± 27.63, post flap creation 509.88± 32.17, one day post-op 468.52± 37.62 and one week post-op 459.23± 35.71. Mean OCT measured central FT values were pre-ablation 128.43± 20.37, one day post-op 112.12± 5.94 and one week post-op 106.75± 8.11. Mean OCT FT values at 1.5 mm from the center were pre-ablation 119.12± 10.48, one day post-op 113.87± 5.99 and one week post-op 108.56± 6.65. Mean OCT FT values at 3.0 mm from the center were pre-ablation 120.93± 10.40, one day post-op 111.68± 5.86 and one week post-op 111.62± 5.21. The difference in mean central CT between pre-operatory and immediately post-flap creation was 28.47 um which was statistically significant (p=0.008).Mean central apical FT significantly decreased at day 1 (-16.31um) and 1 week post-op (-5.37 um) compared to immediately after flap creation (p=0.001).
OCT can be used to monitor intraoperative corneal changes induced by hydration and cavitation bubbles after Femtosecond laser flap creation during LASIK. LASIK flaps were noted to undergo significant thinning at day 1 and one 1 week after surgery. Additional longitudinal follow-up of this patient cohort is required to further characterize flap changes over time.
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