目的：构建和验证基于Sirius眼前节分析仪参数的圆锥角膜早期诊断模型。

方法：该研究包括预测队列中的46只早期圆锥角膜眼(34例患者的20只右眼和26只左眼)和46只年龄和性别相匹配的正常眼(46例患者均为右眼)。基于Sirius的地形图、厚度和像差变量，使用LASSO和Logistic回归分析构建预测指数。应用队列包括23只被Sirius归类为可疑圆锥角膜病例的早期圆锥角膜眼(23例患者的12只右眼和11只左眼)和23只年龄和性别相匹配的正常眼(23例患者均为右眼)。在应用队列中对预测指标进行了外部验证。

结果：Sirius圆锥角膜指数(SKI)是由Sirius角膜最薄点厚度和后表面曲率对称指数计算得出。Logistic回归分析后，SKI在预测队列中具有最高的AUC值(AUC=0.932)。SKI的截止值设定为0.44。随后，详细分析了预测队列的受试者工作特征(ROC)曲线、校准图和诊断公式的列线图。最后，在应用队列中评估了SKI的准确性，其敏感性为91%，特异性为96%。

结论：基于Sirius角膜最薄点厚度和后表面曲率对称指数的SKI是屈光手术术前筛查中早期发现圆锥角膜的一种简单而有效的方法。

METHODS: The study comprised of 46 early keratoconus eyes(including 20 right eyes and 26 left eyes in 34 patients)and 46 age- and gender-matched normal eyes(including the right eyes of 46 patients)in the prediction group. The predictive index was constructed using LASSO and Logistic regression analyses based on the topographic, pachymetric and aberrometry variables of Sirius. There were 23 early keratoconus eyes categorized as suspected keratoconus cases by Sirius(including 12 right eyes and 11 left eyes in 23 patients)and 23 age- and gender-matched normal eyes(including the right eyes of 23 patients)included in the application cohort. External validation of predictors was performed for the application cohort.

RESULTS: Sirius Keratoconus Index(SKI)was calculated based on the minimum corneal thickness and symmetry index back of Sirius. Highest AUC values were obtained in the prediction group(AUC=0.932)after Logistic regression analysis. The cut-off value of SKI was set at 0.44. Then, the receiver operating characteristic(ROC)curve, calibration plot and nomogram of the diagnostic formula were analyzed for the prediction cohort in detail. Finally, the accuracy of the SKI was evaluated in the application cohort; the sensitivity was 91% and the specificity was 96%.

CONCLUSION: SKI based on minimum corneal thickness and symmetry index back of Sirius is a simple and effective method for early detection of keratoconus in the preoperative screening for refractive surgery.