Förster W, Kasprzak H, von Bally G
University Eye Hospital, Münster, Germany.
Optom Vis Sci. 1994 Jan;71(1):27-32. doi: 10.1097/00006324-199401000-00006.
The structural and elastic properties of the cornea play an important role in the outcome of corneal refractive surgery. A way to describe the elastic properties is to calculate Young's modulus. The tangent Young's modulus (Eit) represents the first part of the viscoelastic response of the intact cornea due to intraocular pressure increase.
The tangent Young's modulus (Eit) of the central cornea of 16 fresh enucleated intact bovine eyes determined from the immediate response was calculated by means of holographic interferometry. The stress was an increase of the intraocular pressure. In 16 eyes the change of intraocular pressure was 10 Pa (group I), starting with an intraocular pressure of 1340 Pa (about 10 mm Hg). In 6 of these 16 eyes there was a second pressure increase of 20 Pa starting at the same intraocular pressure of 1340 Pa (about 10 mm Hg) (group II).
The mean value for the Young's modulus in group I was 1.58 x 10(5) Pa. For group II the Young's modulus was 1.60 x 10(5) Pa. The difference was not significant. The values for the Young's moduli of the cornea of intact eyes are about 100 times smaller than calculations based on experiments with strips of the cornea.
It is necessary to consider the localization of the corneal tissue to avoid influences of corneal hydration or dehydration and to define the existing intraocular pressure if Young's modulus of the cornea is to be calculated.
角膜的结构和弹性特性在角膜屈光手术的结果中起着重要作用。描述弹性特性的一种方法是计算杨氏模量。切线杨氏模量（Eit）代表完整角膜因眼内压升高而产生的粘弹性反应的第一部分。
通过全息干涉测量法计算16只新鲜摘除的完整牛眼中央角膜的切线杨氏模量（Eit），该模量由即时反应确定。应力为眼内压升高。在16只眼中，眼内压变化为10帕斯卡（第一组），起始眼内压为1340帕斯卡（约10毫米汞柱）。在这16只眼中的6只，从相同的1340帕斯卡（约10毫米汞柱）眼内压开始，第二次压力升高20帕斯卡（第二组）。
第一组杨氏模量的平均值为1.58×10⁵帕斯卡。第二组杨氏模量为1.60×10⁵帕斯卡。差异不显著。完整眼睛角膜的杨氏模量值比基于角膜条带实验的计算值小约100倍。
如果要计算角膜的杨氏模量，有必要考虑角膜组织的定位，以避免角膜水合或脱水的影响，并确定现有的眼内压。
