Spiru Bogdan, Kling Sabine, Hafezi Farhad, Sekundo Walter
Department of Ophthalmology, Philipps University of Marburg, Marburg, Germany.
Laboratory of Ocular Cell Biology, Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland.
Invest Ophthalmol Vis Sci. 2017 May 1;58(5):2591-2595. doi: 10.1167/iovs.16-20211.
To evaluate the biomechanical stability of ex vivo porcine corneas after femtosecond lenticule extraction (FLEx) and small incision lenticule extraction (SmILE) refractive surgeries.
Forty-five porcine eyes were equally divided into three groups: Groups 1 and 2 were treated with FLEx and SmILE procedure, respectively. Group 3 served as control. A refractive correction of -14 diopters (D) with a 7-mm zone using either a 160-μm flap (FLEx) or a 160-μm cap (SmILE) was performed. For two-dimensional (2D) elastic and viscoelastic biomechanical characterization, two testing cycles (preconditioning stress-strain curve from 1.27 to 12.5 N, stress-relaxation at 12.5 N during 120 seconds) were conducted. Young's modulus and Prony constants were calculated.
At 0.8% of strain, FLEx (370 ± 36 kPa) could resist a significantly lower stress than SmILE (392 ± 19 kPa, P = 0.046) and the control group (402 ± 30 kPa, P = 0.013). Also, FLEx (46.1 ± 4.5 MPa) had a significantly lower Young's modulus than the control group (50.2 ± 3.4 MPa, P = 0.008). The Young's modulus of SmILE (48.6 ± 2.5 MPa) had values situated between untreated corneas and FLEx-treated corneas. When compared to untreated controls, the stress resistance decreased by 8.0% with FLEx and 2.5% with SmILE; Young's modulus decreased by 5.1% with FLEx and 1.04% with SmILE. With a cap-based procedure, both anterior cap and stromal bed carry the intraocular pressure, while in a flap-based procedure, only the stromal bed does.
Compared to flap-based procedures like FLEx, the cap-based technique SmILE can be considered superior in terms of biomechanical stability, when measured experimentally in ex vivo porcine corneas.
评估飞秒透镜切除术（FLEx）和小切口透镜切除术（SmILE）屈光手术后离体猪角膜的生物力学稳定性。
45只猪眼平均分为三组：第1组和第2组分别接受FLEx和SmILE手术。第3组作为对照组。使用160μm的瓣（FLEx）或160μm的帽（SmILE）进行-14屈光度（D）、7mm区域的屈光矫正。为了进行二维（2D）弹性和粘弹性生物力学表征，进行了两个测试循环（从1.27到12.5N的预处理应力-应变曲线，在120秒内12.5N的应力松弛）。计算杨氏模量和普龙尼常数。
在0.8%应变时，FLEx组（370±36kPa）抵抗的应力明显低于SmILE组（392±19kPa，P=0.046）和对照组（402±30kPa，P=0.013）。此外，FLEx组（46.1±4.5MPa）的杨氏模量明显低于对照组（50.2±3.4MPa，P=0.008）。SmILE组（48.6±2.5MPa）的杨氏模量值介于未处理角膜和FLEx处理角膜之间。与未处理的对照组相比，FLEx组的抗应力能力下降了8.0%，SmILE组下降了2.5%；杨氏模量FLEx组下降了5.1%，SmILE组下降了1.04%。在基于帽的手术中，前帽和基质床都承受眼内压，而在基于瓣的手术中，只有基质床承受。
在离体猪角膜上进行实验测量时，与FLEx等基于瓣的手术相比，基于帽的技术SmILE在生物力学稳定性方面可被认为更优越。
