Article
2D-Extensiometry in human corneas after LASIK vs. SMILE: a fellow eye study
Search Medline for
Authors
Published: | February 22, 2018 |
---|
Outline
Text
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.