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G. S. Brar, D. S. Grewal, R. Jain, S. P. S. Grewal; Changes in Elevation and Corneal Volume Following LASIK With Flap Creation Using Intralase, Mechanical Keratome and LASEK. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2441.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate and compare the posterior corneal elevation changes on Pentacam in eyes undergoing LASIK with flap creation using Intralase Femtosecond Laser, mechanical Keratome or flap formation using alcohol in laser-assisted subepithelial keratectomy (LASEK)
60 myopic patients undergoing refractive surgery using VISX Star S4 excimer laser (AMO,Santa Clara, Calif) were prospectively enrolled. 20 patients each underwent flap creation using IntraLase Femtosecond Laser (Group 1), Amadeus Keratome (Group 2) and using 20% alcohol in LASEK (Group 3). Patients underwent Pentacam Scheimpflug Imaging (Oculus, Wetzlar, Germany) using 25 scan image acquisition mode, prior to and at 3 months post-LASIK.Posterior Corneal Elevation data was exported from Pentacam and difference in central 3mm area of cornea comprising a total of 3660 elevation points, pre and post LASIK was calculated. Statistical analysis was performed using paired t-tests and one-way ANOVA. Corneal volume was calculated pre and post LASIK and the change was correlated with ablation depth.
The mean age for the 3 age matched groups was 24.77 ± 6.66 years (Group 1), 26.19± 5.20 years (Group 2) and 26.33 ± 6.11 years (Group 3).The mean change in posterior elevation in the central 3mm area was 2.13 ± 7.16 for Group 1, 4.78 ± 5.42 for Group 2 and 5.68 ± 7.12 for Group 3. The change in elevation was not significant for any of the groups (p=0.342, p=0.232 and p=0.321 for Groups 1,2 and 3 respectively). There was no significant difference in the amount of change in elevation between the three groups (p=0.194).Average decrease in corneal volume was 2.66 ± 1.52 mm3 for Group 1, 2.58 ± 1.26 mm3 for Group 2 and 2.6 ± 2.14mm3 for Group 3. Ablation depth correlated positively with change in corneal volume in all three groups (r=0.536, p=.015; r=0.472, p=0.03; and r=0.456, p=0.007for Groups 1,2 and 3 respectively) The pre-op refraction had a significant negative correlation with ablation depth for all three groups (r= -0.951,p<0.001; r= -0.960, p<0.001 and r= -0.763, p=0.03 for Groups 1,2 and 3 respectively) and with change in corneal volume for Group 1 and 2 (r= -0.479, p=0.038; and r =-0.423, p=0.02 respectively)
There was no significant change in posterior corneal elevation at 3 months post LASIK in any of the 3 methods of flap creation and the amount of shift of posterior cornea was not significantly different among the three methods suggesting that posterior corneal surface was stable. Volume of corneal tissue removed corresponded to the ablation depth.
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