Vanak Eye Surgery Center, Tehran, Iran.
J Refract Surg. 2012 Jan;28(1):59-64. doi: 10.3928/1081597X-20110906-02. Epub 2011 Sep 12.
To investigate the effect of blunt foreign body impact on a human cornea after photorefractive keratectomy (PRK) and LASIK using a simulation model.
Computational simulations were performed using a finite element analysis program (LS-Dyna, Livermore Software Technology Corp). The blunt foreign body was set to impact at the center of the corneal surface models (after PRK and LASIK) with thicknesses of 500, 450, 400, 350, and 300 μm. Corneal rupture was assumed to occur at a peak stress of 9.45 MPa and at a strain of 18%. The foreign body projectile was blunt in shape, made from aluminum, contained plastic-kinematic properties, and had a density of 2700 kg/m(3).
The projectile was launched at the center of the cornea with velocities ranging from 20 to 60 m/s. The threshold of impact velocities creating rupture in corneal thicknesses of 500, 450, 400, 350, and 300 μm were 33, 32.8, 30.7, 27.9, and 22.8 m/s, respectively, in the PRK model. In the LASIK model, the thresholds creating rupture in the stromal bed of the corneas with thicknesses of 500, 450, 400, 350, and 300 μm were 40, 38.1, 35.6, 31.5, and 26.7 m/s, respectively. The 110-μm corneal flap in the LASIK model ruptured at all velocities.
Ruptures occurred at lower velocities in the PRK cornea model than in the corneal stromal bed of the LASIK model following blunt foreign body impact.
利用模拟模型研究准分子激光屈光性角膜切削术（PRK）和 LASIK 后钝性异物撞击对人眼角膜的影响。
使用有限元分析程序（LS-Dyna，Livermore Software Technology Corp）进行计算模拟。将钝性异物设置为撞击 PRK 和 LASIK 后角膜模型中心，角膜厚度分别为 500、450、400、350 和 300μm。假设角膜破裂发生在峰值应力为 9.45MPa 和应变为 18%时。异物弹丸形状钝，由铝制成，具有塑性运动学特性，密度为 2700kg/m³。
以 20 至 60m/s 的速度将弹丸从角膜中心发射。在 PRK 模型中，角膜厚度为 500、450、400、350 和 300μm 时，导致破裂的撞击速度阈值分别为 33、32.8、30.7、27.9 和 22.8m/s。在 LASIK 模型中，角膜基质床厚度为 500、450、400、350 和 300μm 时，导致破裂的撞击速度阈值分别为 40、38.1、35.6、31.5 和 26.7m/s。LASIK 模型中的 110μm 角膜瓣在所有速度下均破裂。
与 LASIK 模型角膜基质床相比，钝性异物撞击后 PRK 角膜模型中的破裂发生在较低的速度下。
