CALCULATION AND APPLICATION OF THE ANTERIOR SURFACE-AREA OF A MODEL HUMAN CORNEA
CALCULATION AND APPLICATION OF THE ANTERIOR SURFACE-AREA OF A MODEL HUMAN CORNEA
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DOI：
10.1016/s0022-5193(84)80072-7
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发表时间：
1984-01-01
影响因子：
2
通讯作者：
KWOK, LS
中科院分区：
文献类型：
--
作者：
KWOK, LS
计算了3种平均人角膜模型的宏观前表面面积。两个模型，一个一般的椭圆和一个旋转椭圆（旋转对称椭圆）给出了132平方毫米的表面积，而球形模型给出了126平方毫米。具有最大水平半径（规则角膜散光）的一般椭圆模型具有比具有相同水平半径的旋转椭圆更小的表面积。对于2.59 mm的角膜矢状高度，椭圆形角膜的表面积等于-19.2Q +16.3R-0.476，这指定了表面积相等的旋转椭圆（半径R，非球面度Q）。在具有最大垂直半径的角膜中（逆规则角膜散光），椭圆体具有比具有相同水平宫颈半径的旋转椭圆略大的表面积。对于给定的水平曲率半径，球体具有最小的表面积。对于2.59 mm的角膜矢状高度s，球面低估了非球面度为-0.5的旋转椭圆的表面积的8%。旋转椭圆模型的前角膜表面积、半径R、非球面度Q由2 π Rs-19.2 Q给出。在所有3个模型中，表面积随着水平曲率半径的增加而增加。在旋转椭圆模型中，增加率（斜率）与非球面性无关，并且在顺规散光中发现的斜率小于在逆规散光中发现的斜率。计算的表面积预测对于6.5 μ m的泪液厚度，角膜前区泪液体积为0.86 μ l。上皮病变的表观或平面投影面积低估了曲面面积，其百分比误差随病变直径迅速增加。对于旋转椭圆模型上直径为12 mm的病变，表观面积低估表面积18%。人类的平均角膜后表面不是球形的，而是模仿前表面，并且具有137 mm 2的面积或比前面积大3.8%。
The macroscopic anterior surface area was calculated for 3 models of the average human cornea. Two models, a general ellipsoid and a rotational ellipse (rotationally symmetric ellipsoid) gave a surface area of 132 mm2, while a spherical model gave 126 mm2. A general ellipsoidal model having the maximum radius horizontal (with-the-rule corneal astigmatism) has less surface area than a rotational ellipse with the same horizontal radius. For a corneal sagittal height of 2.59 mm, the surface area of an ellipsoidal cornea equals -19.2Q + 16.3R - 0.476 which specifies a rotational ellipse (radius R, asphericity Q) of equal surface area. In a cornea with the maximum radius vertical (against-the-rule corneal astigmatism), the ellipsoid has slightly more surface area than a rotational ellipse with the same horizontal radius of cervature. For a given horizontal radius of curvature, the sphere has the lowest surface area. For a corneal sagittal height s of 2.59 mm, the sphere underestimates by 8% the surface area of a rotational ellipse with asphericity -0.5. The anterior corneal surface area of a rotational ellipse model, radius R, asphericity Q is given by 2.pi.Rs - 19.2Q. In all 3 models, the surface area increases with horizontal radius of curvature. In the rotational ellipse model, the rate of increase (slope) is independent of asphericity, and the slope found in with-the-rule astigmatism is less than the slope found with against-the-rule astigmatism. The calculated surface area predicts a precorneal tear volume of 0.86 .mu.l for a 6.5 .mu.m tear thickness. The apparent, or plane projected area of an epithelial lesion underestimates the curved surface area with a percentage error that increases rapidly with lesion diameter. For a 12 mm diameter lesion on a rotational ellipse model, the apparent area underestimates the surfaces area by 18%. The average posterior corneal surface in humans is not spherical but imitates the anterior surface, and has an area of 137 mm2 or 3.8% greater than the anterior area.