方法：本研究收集散光≥2.0D患者107例201眼。所有的患者进行验光、视力、矫正视力、裂隙灯、眼底镜、传统角膜地形图、Pentacam眼前节分析仪检查。观察包括K1：3mm直径范围水平中央曲率，K2：3mm直径范围垂直中央曲率、角膜前表面最大屈光力(Kmax)、角膜散光(CYL)、角膜最薄处的厚度(MinPachy)、表面变异指数(ISV)、垂直不对称指数(IVA)、圆锥角膜指数(KI)、角膜前表面高度(AE)、角膜后表面高度(PE)等指标变化。并作ROC曲线，对比各组的cutoff值及其敏感指标。Pentacam获得的几个参数分析采用Mann-Whitney U检验。通过ROC曲线分析确定出最佳诊断界点。

结果：本研究人群的平均年龄为25.7±6.6岁。前表面Kmax、IVA、KI、AE、PE临床和亚临床组明显高于散光组，角膜最薄处厚度临床和亚临床组明显低于散光组(P<0.05)。Pentacam诊断临床期圆锥角膜的敏感指标(曲线下面积AUC≥0.9)，分别为AE、PE、IVA、ISV、KI、Kmax。诊断亚临床圆锥角膜的敏感指标(曲线下面积AUC≥0.9)为PE。

结论：研究表明，2D以上散光的人群即使视力正常，也应该进行角膜地形图筛查。Pentacam眼前节分析仪可以提供精准的角膜前后表面解剖信息，尤其是角膜后表面高度测定，对亚临床期圆锥角膜的筛查起重要作用。

METHODS: Two hundred and one eyes in 107 patients with astigmatism ≥2D were included in this study. All patients underwent optometry, visual acuity, corrected visual acuity, slit lamp biomicroscopy, fundus examination, traditional corneal topography and examination with Pentacam. Changes of several parameters were observed including K1(horizontal central curvature within the scope with diameter of 3mm), K2(vertical central curvature within the scope with diameter of 3mm); Kmax(the maximum anterior corneal refractive power), corneal astigmatism(CYL), MinPachy(the thickness at the thinnest area of cornea), index of surface variation(ISV), index of vertical asymmetry(IVA), keratoconus index(KI), height of anterior corneal surface(AE)and height of posterior corneal surface(PE), etc. ROC curve was made. Cutoff value and the sensitive index of each group were compared. Mann-Whitney U test was used for analysis of several parameters obtained from Pentacam. ROC curve was analyzed to determine the best diagnosis cutoff value.

RESULTS: Mean age of the study population was 25.7±6.6 years old. Kmax, IVA, KI, AE and PE of the clinical and subclinical group were significantly higher than those of the astigmatism group, while the thickness at the thinnest area of cornea in clinical and subclinical group was lower than that of the astigmatism group(P<0.05). Sensitive index of Pentacam to diagnose keratoconus at clinical stage \〖the area under the curve(AUC)≥0.9\〗 were AE, PE, IVA, ISV, KI, Kmax, respectively. Sensitive index for the diagnosis of subclinical keratoconus \〖the area under the curve(AUC)≥0.9\〗 was PE.

CONCLUSION: The current study shows that subjects with 2D or more of astigmatism, even some of them have normal vision, should undergo corneal topography screening. Pentacam may provide more accurate information about anterior and posterior corneal anatomy especially for the height of posterior corneal surface, which plays an important role in screening of subclinical KCN.