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32. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation, Interventionelle und Refraktive Chirurgie (DGII)

Deutschsprachige Gesellschaft für Intraokularlinsen-Implantation, Interventionelle und Refraktive Chirurgie (DGII)

15.02. - 17.02.2018, Dresden

2D-Extensiometry in human corneas after LASIK vs. SMILE: a fellow eye study

Meeting Abstract

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  • Bogdan Spiru - Marburg
  • S. Kling - Laboratory of Ocular Cell Biology, Center for Applied Biotechnology and Molecular Medicine, University of Zürich/CH
  • F. Hafezi - Laboratory of Ocular Cell Biology, Center for Applied Biotechnology and Molecular Medicine, University of Zürich/CH; ELZA Institute, Dietikon/CH; Los Angeles/USA
  • W. Sekundo - Marburg

Deutschsprachige Gesellschaft für Intraokularlinsen-Implantation, Interventionelle und Refraktive Chirurgie. 32. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation, Interventionelle und Refraktive Chirurgie (DGII). Dresden, 15.-17.02.2018. Düsseldorf: German Medical Science GMS Publishing House; 2018. Doc18dgii038

doi: 10.3205/18dgii038, urn:nbn:de:0183-18dgii0385

Published: February 22, 2018

© 2018 Spiru et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at http://creativecommons.org/licenses/by/4.0/.


Outline

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Purpose: To investigate the biomechanical properties of the ex-vivo human cornea after flap-based vs. cap-based laser refractive surgery in the same donor.

Design: Experimental study

Methods: 11 pairs of human corneas were equally divided into 2 groups: Corneas from right eye were treated with LASIK and corneas from the left eye with SmILE procedure, respectively. Pachymetry was measured in each eye directly before laser refractive surgery. All corneas were subjected to a refractive correction of -10 dpt sphere and -0.75 dpt cylinder with a 7mm zone using either a 110µm flap (LASIK) or 130µm cap (SmILE). For 2D-biomechanical measurements, corneo-scleral buttons were excised. Two testing cycles (pre-conditioning stress-strain curve from 0.03 to 9.0 N, stress-relaxation at 9.0 N during 120s) were performed in order to analyze the elastic and viscoelastic material properties. The effective Young’s modulus was calculated. Statistical analysis was performed with a confidence interval of 95%.

Results: In stress-strain measurements, the effective Young’s modulus was 1.47 times higher (p=0.003) after SmILE (median=8.22 [IQR=4.76] Mpa) compared to LASIK (median=5.59 [IQR=2.77] Mpa) refractive correction. The effect size was large (r=0.83). No significant differences (p=0.658) were observed among stress-relaxation measurements, with a mean remaining stress of 181(+/- 31) kPa after SmILE and 177(+/- 26) kPa after LASIK after relaxation.

Conclusions: Compared to a flap-based procedure like LASIK, the SmILE technique can be considered net superior in terms of biomechanical stability, when measured experimentally in ex-vivo human fellow eye corneas.