Objective To compare the corneal biomechanical properties between keratoconic eyes and normal eyes by using corneal visualization Scheimpflug technology (Corvis ST),and to evaluate the diagnostic value of corneal biomechanical parameters based on Corvis ST in keratoconus.Methods A prospective cases-control study was performed.Twenty-four keratoconic eyes from 17 patients and 40 normal eyes (right eye) from 40 participants were enrolled from October to December in Peking University First Hospital.Anterior segment parameters and refractive diopters were obtained with Topography (TMS-4) and mydriatic refraction.Biomechanical parameters were assessed with Corvis ST.Independent sample t-test and Wilcoxon rank sum test were used to compare the parameters of the two groups.The receiver operating characteristic (ROC) curves were plotted to distinguish keratoconus from the normal cornea.Diagnostic efficacies of all parameters were analyzed and some parameters were used as independent variables to establish a Logistic regression model.Results Maximum deformation amplitude of highest concavity (HCDA),maximum corneal velocity during the second applanation (Vout) and distance between both non-deformed peaks (PD) in the keratoconus group were higher than those in the normal control group,and first applanation time (A1T),cord length of first applanation (ALL),cord length of second applanation (A2L),radius value of central concave curvature at highest concavity (HCR) were lower than those in the normal control group,with significant differences between the two groups (all at P＜0.05).Maximum corneal velocity during the first applanation (Vin),second applanation time (A2T) and time taken to reach highest concavity (HCT) were insignificantly different between the two groups (all at P＞0.05).Many parameters had diagnostic values in keratoconus assessed by ROC analysis.HCR was the most efficient parameter showed by ROC evaluation (area under the curve was 0.927,sensitivity was 95.8％,specificity was 82.5％).The Logistic model were established with two independent variables,HCR (OR=0.205) and central corneal thickness (CCT) (OR=0.970).The forecast model of keratoconus diagnosis was established as follows:Logistic (P) =23.47-1.59×HCR-0.30×CCT.Diagnostic sensitivity and specificity were enhanced by using this model,the sensitivity was 95.8％,and the specificity was 95.0％.Conclnsions It is useful to evaluate the corneal biomechanical properties with Corvis ST.HCR is an efficient auxiliary testing index of diagnosis or screening of keratoconus.%目的 应用可视化角膜生物力学分析仪(Corvis ST)对圆锥角膜与正常角膜生物力学参数的差异进行比较分析,探讨基于Corvis ST的角膜生物力学参数在圆锥角膜诊断中的价值.方法 本研究为前瞻性病例对照研究.连续收集2015年10-12月于北京大学第一医院门诊就诊的圆锥角膜患者17例24眼作为圆锥角膜组,同期招募正常志愿者40人40眼为正常对照组.应用Corvis ST测量2个组人群的角膜生物力学参数并进行比较;绘制受试者工作特征(ROC)曲线,分析各参数对圆锥角膜的诊断效率及其特异度与敏感度;将各参数作为自变量,建立Logistic回归模型,对圆锥角膜的诊断进行多因素分析. 结果 除第一次压平速度(Vin)、第二次压平时间(A2T)和最大压陷时间(HCT)这3个参数外,圆锥角膜组最大压陷深度(HCDA)、第二次压平速度(Vout)、两峰间距(PD)均高于正常对照组,第一次压平时间(A1T)、第一次压平长度(A1L)、第二次压平长度(A2L)、最大压陷时角膜曲率半径(HCR)均低于正常对照组,差异均有统计学意义(均P＜0.05).ROC曲线分析显示,多种生物力学参数均对圆锥角膜具有诊断意义,其中,HCR的诊断效率最高,曲线下面积为0.927,敏感度为95.8％,特异度为82.5％;HCR(OR=0.205)和中央角膜厚度(CCT)(OR=0.970)2个参数作为自变量进入回归模型,建立圆锥角膜诊断的预测模型如下:Logistic (P)=23.47-1.59×HCR-0.30×CCT,该模型可进一步提高圆锥角膜诊断的敏感性(达到95.8％)和特异性(达到95.0％). 结论 Co.is ST可有效测量角膜生物力学特性.HCR等多种参数对圆锥角膜具有诊断意义,可考虑作为诊断/筛查圆锥角膜的辅助检测指标.
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