Biomechanical properties of human cornea tested by two-dimensional extensiometry ex vivo in fellow eyes: PRK vs SMILE

Session Details

Session Title: Corneal Biomechanics

Session Date/Time: Sunday 15/09/2019 | 16:30-18:00

Paper Time: 17:48

Venue: Free Paper Forum: Podium 4

First Author: : W.Sekundo GERMANY

Co Author(s): :    B. Spiru   S. Kling   E. Torres-Netto   A. Lazaridis   F. Hafezi                 

Abstract Details

Purpose:

To investigate the biomechanical properties of the ex vivo human cornea after photorefractive keratectomy versus small incision lenticule extraction refractive surgery in the same donor.

Setting:

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 keratectomy (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.

Financial Disclosure:

receives non monetary benefits from a company producing, developing or supplying the product or procedure presented