Artikel
Biomechanical analysis of different retreatment options after SMILE refractive surgery
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Veröffentlicht: | 15. Februar 2017 |
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Gliederung
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Purpose: To determine the corneal weakening induced by different re-treatment options after SmILE, and to investigate the potential of corneal cross-linking (CXL) to re-establish the original corneal stress resistance.
Methods: A total of 96 freshly enucleated porcine corneas were used. The initial refractive correction was defined to be -11D and the required enhancement to be -3D. Three different retreatment options were analyzed: (i) -3D Re-SmILE, (ii) -3D PRK on top of the SmILE cap and (iii) cap-to-flap conversion and -3D excimer ablation on the stromal bed (“LASIK”). The (iv) control condition did not receive any treatment. Subsequently, accelerated CXL (9mW/cm2, 10min) was performed in two groups with currently common enhancement techniques: (v) following cap-to-flap conversion (-3D “LASIK” enhancement) and (vi) in controls. Biomechanical properties were measured with stress-strain extensometry in the range from 1.27 to 12.5N.
Results: The Re-SmILE and PRK enhancement did not significantly reduce the overall elastic modulus of the cornea compared to controls (24.7 Mpa and 22.7 Mpa versus 23.8 Mpa, p=0.176), while LASIK enhancement did (22.2 Mpa, p=0.048). CXL treatment significantly increased the elastic modulus compared to all non-cross-linked conditions (p 0.001). Refractive surgery decreased the overall elastic modulus by 7%, while CXL increased it by 20%.
Conclusions: In enhancement, the corneal biomechanical integrity is less affected with both, Re-SMILE and PRK enhancement. Corneal weakening through laser refractive surgery is small compared to the stiffening effect after CXL.