近视眼角膜上皮厚度分布特点及其与角膜生物力学性能的关系

Corneal epithelial thickness in myopic eyes and its relationship with the corneal biomechanical properties

目的 分析近视眼角膜不同区域的上皮厚度分布特点及其与角膜生物力学等因素的关系.方法 横断面研究.选取拟行准分子激光角膜屈光手术的近视及近视散光患者198例（198眼）,年龄18～41岁,等效球镜度-0.75～-10.38 D,将右眼数据纳入分析.应用RTVue眼前节OCT测量角膜中央0～2 mm直径区域平均上皮厚度,周边＞2～5 mm及＞5～6 mm 2个区域角膜上方、颞上方、颞侧、颞下方、下方、鼻下方、鼻侧、鼻上方等象限的上皮厚度.将角膜中央上皮按照厚度不同分为3组,应用眼反应分析仪（ORA）测量角膜滞后量（CH）、角膜阻力因子（CRF）,分析其与上皮厚度的关系.应用Mann-Whitney U检验、Kruskal-Wallis检验、多元线性回归分析、Spearman相关分析等方法对所测结果进行分析.结果 角膜0～～2 mm,＞2～5 mm,＞5～6 mm区域上皮厚度分别为54.0 （52.0～56.0）μm,54.1 （52.6～56.4）μm,53.8（52.2～55.8）μm,区域之间差异无统计学意义（Z=3.860,P＞0.05）.角膜8个象限之间的上皮厚度差异有统计学意义（Z＞2-5mm=279.482,P＜0.01;Z＞5-6mm=210.442,P＜0.01）,其中,上方（颞上方、上方、鼻上方）的上皮厚度明显比下方（颞下方、下方、鼻下方）薄（Z＞2-5mm=-5.243,P＜0.01,Z＞5-6mm=-8.101,P＜0.01）,鼻侧与颞侧差异无统计学意义（Z＞2-5mm=-0.481,P＞0.05,Z＞5-6mm=-0.381,P＞0.05）.随着角膜上皮厚度的增加,角膜的生物力学性能会相应地增强;不同角膜中央上皮厚度组间CH与CRF差异均有统计学意义（CH：Z=8.945,P＜0.05;CRF：Z=9.225,P＜0.05）.角膜中央上皮厚度与年龄呈负相关,即年龄越大,角膜上皮厚度越薄（r=-0.185,P＜O.0）;与屈光度不相关（r=-0.092,P＞0.05）.结论 近视眼角膜上皮呈非均匀分布,除上方较下方偏薄外,各象限也存在厚度差异;角膜上皮对角膜生物力学性能有一定影响,角膜上皮越厚,相应的生物力学性能越强.

Objective To measure the corneal epithelial thickness in myopic eyes, and to study the relationship between corneal epithelial thickness and biomeehanieal properties. Methods In this cross-sectional study, 198 right eyes of 198 myopia or myopic astigmatism patients were enrolled. The age was 18-41 years old. The equivalent spherical refraction was -0.75--10.38 D. Corneal epithelial thickness for different corneal zones （0-2 mm, 〉2-5 ram, 〉5-6 mm） was measured using RTVue-OCT. Different quadrant epithelial thickness, including the superior, superior temperal, temporal, inferior temperal, inferior, inferior nasal, nasal, superior nasal of the cornea, were obtained. Correlations of corneal epithelial thickness with corneal hysteresis （CH） and corneal resistance factor （CRF）, which were measured by ORA, were investigated. Three groups were divided according to the different corneal epithelial thickness. Mann-Whitney U test, Krnskal-Wallis test, multivariable linear regression method were used to analyze the data. Results The 0-2 mm, 〉2-5 mm, 〉5-6 mm corneal epithelial thickness median of the 198 eyes were 54.0（52.0-56.0）μm, 54.1（52.6-56.4）μm, 53.8（52.2-55.8）μm, respectively. No relationships were found among the three corneal zones （Z=3.860, P〉0.05）. While a statistically significant correlation was found among the eight quadrants（Z〉2-5mm=279.482, P〈0.01; Z〉5-6mm=210.442, P〈0.01）. The corneal epithelium was thinner superiorly than inferiorly （Z〉2-5mm=-5.243, P〈0.01, Z〉5-6mm=-8.101, P〈0.01）, no significant differences was found between nasall and temporal （Z〉2-5mm=-0.481, P〉0.05, Z〉5-6mm=-0.381, P〉0.05）. Positive relationships were found between the central corneal epithelial thickness with CH and CRF. The statistically significant different were found in three corneal epithelial thickness groups （CH： Z=8.945, P〈0.05; CRF： Z=9.225, P〈0.05）. Positive relationships were also found between the central corneal epithelial thickness and the age （r=-0.185, P〈0.01 ）. No relationships were found between the central corneal epithelial thickness and the diopter （r=-0.092, P〉0.05）. Conelusion The corneal epithelial thickness is not evenly distributed across the cornea. The epithelial thickness has a positive correlation with the corneal biomeehanical properties.