Lu Nan-Ji, Jiménez-García Marta, Elsheikh Ahmed, Makarem Ahmed, Koppen Carina, Rozema Jos J
Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, China.
Visual Optics Lab Antwerp (VOLANTIS), Faculty of Medicine and Health Sciences, University of Antwerp, Wilrijk, Belgium.
Transl Vis Sci Technol. 2025 Mar 3;14(3):23. doi: 10.1167/tvst.14.3.23.
The purpose of this study was to compare the performance of the Stress-Strain Index versions 1 and 2 (SSI and SSI2) in healthy patients and patients with keratoconus (KC).
Fifty-two healthy and 104 KC eyes were examined using Scheimpflug-based tomography and air-puff tonometry (Pentacam and Corvis). Correlations between both versions of SSI and age, thinnest pachymetry, and tomographic parameters were assessed. To discriminate KC eyes from healthy eyes, receiver operating characteristic curves were generated to calculate the area under the curve (AUC) for both versions of SSI and compared with a Delong test.
Both versions of SSI showed statistical differences between the healthy group and the group of patients with KC (all P < 0.001). In the healthy group, significant correlations were found between both versions of SSI and age, K1, K2, and Kmax, between SSI and average relational thickness (ART) Max (R2 = 0.23) and between SSI2 and Belin A (R2 = 0.08). In the KC group, significant correlations were found between both versions of SSI and all tomographic parameters (all P < 0.01, except for SSI2 with age P = 0.346); the R2 values in SSI2 were consistently higher than in SSI. AUC for SSI and SSI2 when comparing normal and KC eyes was 0.772 and 0.740, respectively (P = 0.468).
Both versions of SSI correlated with tomographic parameters describing KC severity, but correlations were higher for SSI2 and were not affected by age. Both versions demonstrated the same diagnostic ability for KC.
Both versions of SSI are not interchangeable, SSI2 may be preferred to depict the corneal stiffness.
本研究旨在比较应力应变指数1版和2版（SSI和SSI2）在健康患者和圆锥角膜（KC）患者中的表现。
使用基于Scheimpflug的断层扫描和气流眼压计（Pentacam和Corvis）对52只健康眼睛和104只KC眼睛进行检查。评估了两个版本的SSI与年龄、最薄角膜厚度以及断层扫描参数之间的相关性。为了区分KC眼睛和健康眼睛，生成了受试者操作特征曲线，以计算两个版本的SSI的曲线下面积（AUC），并通过Delong检验进行比较。
两个版本的SSI在健康组和KC患者组之间均显示出统计学差异（所有P < 0.001）。在健康组中，两个版本的SSI与年龄、K1、K2和Kmax之间存在显著相关性，SSI与平均相对厚度（ART）Max之间存在显著相关性（R2 = 0.23），SSI2与Belin A之间存在显著相关性（R2 = 0.08）。在KC组中，两个版本的SSI与所有断层扫描参数之间均存在显著相关性（除SSI2与年龄P = 0.346外，所有P < 0.01）；SSI2中的R2值始终高于SSI。比较正常眼睛和KC眼睛时，SSI和SSI2的AUC分别为0.772和0.740（P = 0.468）。
两个版本的SSI均与描述KC严重程度的断层扫描参数相关，但SSI2的相关性更高且不受年龄影响。两个版本对KC均具有相同的诊断能力。
两个版本的SSI不可互换，SSI2可能更适合描述角膜硬度。
