摘要目的 了解正常角膜和圆锥角膜的角膜滞后量(CH)和阻力因子量(CRF),探讨圆锥角膜形态和结构改变后对角膜生物力学特性的影响.方法 病例对照研究.选取同时期46只圆锥角膜眼作为圆锥角膜组,96只正常角膜眼作为对照组.用眼反应分析仪(ORA)测定两组眼的CH和CRF,并进行比较分析.其中对照组按角膜散光又分为高度散光(≥3.00 D)和中低度散光(<3.00 D);圆锥角膜组按Amsler-Krumeich法分为轻度(Ⅰ级)、中度(Ⅱ级)和重度(Ⅲ/Ⅳ级).对组间CH和CRF差异比较采用t检验或单因素方差分析.CH和CRF与中央角膜厚度,角膜曲率,角膜散光以及后表面高度间进行直线相关和多重回归分析,绘制CH和CRF的接受者工作特征(ROC)曲线.结果 CH和CRF在圆锥角膜组为(7.1±1.6)和(6.3±1.5)mm Hg(1 mm Hg=0.133 kPa),明显低于对照组的(10.1±1.3)和(10.5±1.6)mm Hg(t=-11.813,-14.943;P<0.001),分别下降(3.0±0.3)和(4.2±0.3)mm Hg.CH和CRF在对照组中的高度角膜散光和中低度角膜散光组之间差异无统计学意义(t=0.373,0.095;P>0.05).CH和CRF大小与圆锥角膜病变程度呈负相关(r=-0.627,-0.587;P<0.001).多重线性回归分析中,圆锥角膜组CH与角膜厚度和曲率相关(r=0.320,-0.375;P<0.05),CRF与角膜曲率相关(r=-0.441,P<0.01),而在对照组中两者与角膜厚度显著相关(r=0.367,0.459;P<0.001),与角膜曲率、散光无关(P>0.05).CH与CRF的ROC曲线下面积分别为0.9282和0.9731(Z=20.462,38.305;P<0.0001),两者之间差异有统计学意义(Z=7.134,P=0.008).结论 圆锥角膜的CH和CRF较正常角膜明显降低,尤以CRF更明显.对CH和CRF进行长期随访,有助于评估圆锥角膜的病变进程.CH和CRF可纳入诊断圆锥角膜的辅助检测指标.

abstractsObjective To compare the corneal hysteresis (CH) and corneal resistance factor (CRF) measured with the Ocular Response Analyzer (ORA) in normal and keratoconic eyes. Methods It was a case-control study. Random selected 96 normal eyes and 46 keratoconic eyes in the same period were included in this study. Normal eyes were divided into 2 groups: high corneal astigmatism (≥3.00 D) and low-to-moderate corneal astigmatism (<3.00 D). Keratoconic eyes were also divided into 3 groups based on Amsler-Krumeich classification: mild (stage Ⅰ), moderate (stage Ⅱ) and severe (stage Ⅲ/Ⅳ). CH and CRF were compared between groups and the areas under ROC curves of the CH and CRF were calculated. Results The mean CH and CRF were (7.1±1.6) mm Hg and (6.3±1.5) mm Hg in keratoconic eyes compared with (10.1±1.3) mm Hg and (10.5±1.6) mm Hg in normal eyes. The difference were statistically significant(t=-11.813, -14.943 ;P<0.001). In normal eyes, there was no difference of CH or CRF between the high corneal astigmatism and low-to- moderate corneal astigmatism (t=0.373,0.095; P>0.05). In keratoconic eyes, there was a significant negative correlation between CH and the keratoconus grade (r=-0.627, P<0.001) and the same relationship was found between CRF and the keratoconus grade (r=-0.587, P<0.001). In multiple linear regression analysis, CH was correlated with central corneal thickness (CCT) and corneal curvature (r=0.320, -0.375;P<0.05) and CRF was correlated with corneal curvature in keratoconic eyes (r=-0.441 ,P<0.01), while they were only correlated with CCT in normal eyes (r=0.367,0.459;P<0.001). The areas under ROC curves of the CH and CRF were 0.9282 and 0.9731 (Z=20.462,38.305 ;P<0.0001), the difference between them was significant (Z =7.134,P=0.008). Conclusions The CH and CRF were significantly lower in keratoconic eyes than in normal eyes, especially on CRF. The long-term follow-up of CH and CRF may provide information for evaluation of progression of keratoconus. They may be included as indicators for detecting keratoconus.