目的：探讨角膜应力-应变指数(SSI)结合角膜生物力学参数诊断早期圆锥角膜的价值。

方法：回顾性研究。纳入2022年3月至2024年2月我院诊治的早期圆锥角膜患者34例53眼，选取同期我院体检正常的志愿者112名112眼(纳入左眼入组)作为健康对照组。使用Corvis ST设备测量，并由Scheimpflug相机记录形变，获取10项生物力学参数\〖首次压平时间(A1T)、首次压平长度(A1L)、首次压平速度(Vin)、二次压平时间(A2T)、二次压平长度(A2L)、二次压平速度(Vout)、最大压陷时间(HCT)、最大压陷深度(HCDA)、最大压陷时角膜曲率(HCR)、两峰间距(PD)\〗和应力-应变指数(SSI)。比较两组参与者的角膜生物力学参数。采用Logistic回归分析影响圆锥角膜发病的危险因素，并绘制ROC曲线分析角膜生物力学参数对早期圆锥角膜诊断效能。

结果：圆锥角膜组患者SSI(0.77±0.17)低于健康对照组(1.01±0.24)(P<0.001)。圆锥角膜组患者A1T、A1L、A2L、HCR低于健康对照组，Vout、HCDA、PD高于健康对照组(均P<0.001)。Logistic回归分析显示SSI、A1T、A1L、A2L、HCR下降及Vout、HCDA、PD升高均是影响圆锥角膜发病的危险因素(P<0.001)。ROC曲线分析显示联合诊断早期圆锥角膜的AUC值为0.997，约登指数为0.954，敏感度、特异度分别为98.1%、97.3%，95%CI为0.994-1.000。

结论：SSI结合角膜生物力学参数对早期圆锥角膜具有诊断意义，且联合诊断价值更高，可考虑作为早期圆锥角膜诊断或筛查指标。

METHODS:A retrospective study was conducted on 34 patients(53 eyes)with early keratoconus diagnosed and treated in our hospital from March 2022 to February 2024. Additionally, 112 normal volunteers(112 eyes)who underwent physical examinations in our hospital during the same period were selected as a healthy control group. The CorvisST equipment was utilized for measurement and recorded deformation with Scheimpflug camera to obtain 10 biomechanical parameters: first applanation time(A1T), first applanation length(A1L), velocity of initial applanation(Vin), second applanation time(A2T), second applanation length(A2L), velocity of outward applanation(Vout), highest concavity time(HCT), highest concavity depth of applanation(HCDA), highest concavity radius(HCR), and peak distance(PD), as well as stress-strain index(SSI), and the corneal biomechanical parameters of the two groups were compared. Furthermore, Logistic regression analysis was used to identify the risk factors for keratoconus, and ROC curves were plotted to analyze the biomechanical parameters of the cornea for early diagnosis of keratoconus.

RESULTS:The SSI(0.77±0.17)in patients with keratoconus was lower than that in healthy controls(1.01±0.24; P<0.001). Patients with keratoconus had lower A1T, A1L, A2L, and HCR, and higher Vout, HCDA, and PD compared to healthy controls(all P<0.001). Logistic regression analysis showed that decreased SSI, A1T, A1L, A2L, and HCR, as well as increased Vout, HCDA, and PD, were risk factors for the development of keratoconus(P<0.001). ROC curve analysis showed that the AUC value for combined diagnosis of early keratoconus was 0.997, with a Youden's index of 0.954, sensitivity and specificity of 98.1% and 97.3%, respectively, and a 95% CI of 0.994-1.000.

CONCLUSION:The combination of SSI and corneal biomechanical parameters holds diagnostic significance for early keratoconus, and the joint diagnostic value is even higher. It can be considered as a diagnostic or screening indicator for early keratoconus.