近视眼角膜前表面的非球面性

Corneal asphericity in myopia

目的应用Orbscan-Ⅱ角膜地形图仪研究近视眼角膜前表面的非球面特性。方法对正视和近视成人共156例249眼行角膜地形图检查及主觉验光。按照等效球镜分成正视组(-0.25～+0.50D)、低度近视组(-0.37～-3.00D)、中度近视组(-3.12～-6.00D)和高度近视组(>-6.00D)。对所得角膜地形图参数中角膜非球面参数(Q值)进行方差分析。结果样本总体Q值平均为-0.23±0.13(-0.69～0.00),组间Q值差异有统计学意义(P<0.01),但在近视的三组之间Q值差异无统计学意义(P>0.05)。结论角膜形态为扁长椭圆形,从中央到周边逐渐平坦;近视性屈光不正可导致角膜非球面性的改变。

Objective The corneal characters are altered following excimer laser refractive surgery. It is necessary to simplify the corneal shape as an ellipse section by a mathematical model in order to describe the unspherical characters. In this study,we analyzed corneal asphericity in myopia. Methods Corneal topography was obtained from 249 eyes of 156 adults with Orbscan-Ⅱ corneal topographic system. According to spherical equivalent （SE）, subjects were divided into emmetropic group （ ranged from - 0.25 to ＋ 0.50 D） ,low myopic group （ ranged from - 0.37 to - 3.00 D） , moderate myopic group （ ranged from - 3.12 to - 6.00 D） and high myopic group（ 〉 - 6.00 D）. The corneal asphericity（Q） and refractive error was analyzed with ANOVA. Results The mean asphericity value was - 0.23 ± 0.13 （ ranged from - 0. 69 to 0.00）. All the values corresponded to the mathematical description of the prolate ellipse, and most commonly accepted for the normal human cornea, A significant difference was seen in asphericity value among emmetropic,tow myopic,moderate myopic arid high myopic groups（F = 4. 636,P = 0. 004） as well as between low myopic, moderate myopic, high myopic group and emmetropic group （P 〈 0. 01 ）. However, there was no significant difference was found between different myopic groups （ P 〉 0. 05 ）. Conclusion The asphericity values support the generalized morphology of tbe prolate cornea as tbe standard. Tbese results suggest that there may be differences between emmetropic and myopic eyes with regard to the anterior segment changes that occur during refractive error development.