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

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

14. - 16.02.2019, Berlin

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Biomechanical Properties of Human Cornea Tested by Two-Dimensional Extensiometry Ex Vivo in Fellow Eyes: PRK vs. SMILE

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  • Bogdan Spiru - Marburg
  • S. Kling - O.P.T.I.C., Computer Vision Laboratory, Swiss Federal Institute of Technology, Zürich, Schweiz
  • E. Torres - Zürich, Schweiz
  • A. Lazaridis - Marburg
  • F. Hafezi - Zürich, Schweiz
  • W. Sekundo - Marburg

Deutschsprachige Gesellschaft für Intraokularlinsen-Implantation, Interventionelle und Refraktive Chirurgie. 33. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation, Interventionelle und Refraktive Chirurgie (DGII). Berlin, 14.-16.02.2019. Düsseldorf: German Medical Science GMS Publishing House; 2019. Doc19dgii035

doi: 10.3205/19dgii035, urn:nbn:de:0183-19dgii0357

Published: March 1, 2019

© 2019 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 photorefractive keratektomy versus lenticle extraction refractive surgery in the same donor.

Setting/venue: In this experimental study, 13 pairs of human corneas unsuitable for transplantation were equally divided into two groups. Corneas from the right eye were treated with photorefractive keratektomy (PRK) and corneas from the left eye with small incision lenticule extraction (SMILE).

Methods: Pachymetry was measured in each eye directly before laser refractive surgery. All corneas were subjected to a refractive correction of -10.00 diopters (D) sphere and -0.75 D cylinder at 0° with a 7 mm zone, using either surface ablation (PRK) or 130 µm cap (SMILE). For two-dimensional biomechanical measurements, corneoscleral buttons underwent two testing cycles (preconditioning stress-strain curve from 0.03 to 9.0 N and stress-relaxation at 9.0 N during 120 sec) to analyze the elastic and viscoelastic material properties. The effective elastic modulus was calculated. Statistical analysis was performed with a confidence interval of 95%.

Results: In stress-strain measurements, the effective elastic modulus was not significantly different (P = .133) between SMILE (mean = 9.58 [standard deviation = 4.26] MPa) and PRK (mean = 11.9 [standard deviation= 4.90] MPa). The effect size was medium (cohen’s d = 0.58). Also, in stress-relaxation measurements, the remaining stress was not significantly different (P=.878) between SMILE (mean=122 [standard deviation = 33] kPa) and PRK (mean=123 [standard deviation = 30] kPa).

Conclusions: Lenticle extraction procedure (SMILE) and the surface ablation technique (PRK) can be considered equal in terms of biomechanical stability, when measured experimentally in ex vivo human fellow eye corneas.