Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil.
Ophthalmology. 2010 Apr;117(4):673-9. doi: 10.1016/j.ophtha.2009.09.023.
To compare corneal hysteresis (CH), corneal resistance factor (CRF), spherical equivalent (SE), average central keratometry (K-Avg), corneal astigmatism (CA), corneal volume (CV), anterior chamber (AC) depth, and central corneal thickness (CCT) between patients with mild keratoconus and healthy controls and to estimate the sensitivity and specificity of CH and CRF in discriminating mild keratoconus from healthy corneas.
Comparative case series.
Sixty-three eyes (40 patients) with mild keratoconus (group 1) and 80 eyes from 40 gender- and age-matched controls (group 2).
Patients underwent a complete clinical eye examination, corneal topography (Humphrey ATLAS; Carl Zeiss Meditec, Dublin, CA), tomography (Pentacam; Oculus, Wetzlar, Germany), and biomechanical evaluations (ocular response analyzer; Reichert Ophthalmic Instruments, Depew, NY). The receiver operating characteristic (ROC) curve was used to identify cutoff points that maximized sensitivity and specificity in discriminating mild keratoconus from normal corneas.
Corneal hysteresis, CRF, SE, K-Avg, CA, CV, AC depth, and CCT. The diagnostic performance of CH and CRF for detecting mild keratoconus was assessed using the ROC curve.
In group 1 versus group 2, the SE values (mean+/-standard deviation) were -3.55+/-2.87 diopters (D) versus -1.46+/-3.09 D (P = 0); K-Avg, 45.09+/-2.24 versus 43.24+/-1.54 D (P = 0); CA, 3.15+/-1.87 versus 1.07+/-0.83 D (P = 0); CV, 57.3+/-2.12 versus 60.86+/-3.39 mm3 (P = 0); AC depth, 3.19+/-0.35 versus 3.05+/-0.43 mm (P = 0.0416); CCT, 503+/-34.15 versus 544.71+/-35.89 microm (P = 0); CH, 8.50+/-1.36 versus 10.17+/-1.79 mmHg (P = 0); CRF, 7.85+/-1.49 versus 10.13+/-2.0 mmHg (P = 0). The ROC curve analyses showed a poor overall predictive accuracy of CH (cutoff, 9.64 mmHg; sensitivity, 87%; specificity, 65%; test accuracy, 74.83%) and CRF (cutoff, 9.60 mmHg; sensitivity, 90.5%; specificity, 66%; test accuracy, 76.97%) for detecting mild keratoconus.
The values for CH, CRF, CV, and CCT were statistically lower and those for SE, K-Avg, CA, and AC depth were statistically higher in patients with mild keratoconus compared with controls. Corneal hysteresis and CRF were poor parameters for discriminating between mild keratoconus and normal corneas.
FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.
比较轻度圆锥角膜患者和健康对照者的角膜滞后（CH）、角膜阻力因子（CRF）、等效球镜（SE）、平均中央角膜曲率（K-Avg）、角膜散光（CA）、角膜体积（CV）、前房深度和中央角膜厚度（CCT），并评估 CH 和 CRF 区分轻度圆锥角膜与正常角膜的敏感性和特异性。
病例对照研究。
63 只眼（40 例患者）为轻度圆锥角膜（第 1 组），80 只眼来自 40 例性别和年龄匹配的对照者（第 2 组）。
患者接受完整的临床眼部检查、角膜地形图（Humphrey ATLAS；卡尔蔡司 Meditec，都柏林，CA）、断层扫描（Pentacam；Oculus，韦茨拉尔，德国）和生物力学评估（眼反应分析仪；Reichert 眼科仪器，迪普韦尔，NY）。使用受试者工作特征（ROC）曲线确定最大程度提高轻度圆锥角膜与正常角膜之间区分灵敏度和特异性的截断值。
CH、CRF、SE、K-Avg、CA、CV、AC 深度和 CCT。使用 ROC 曲线评估 CH 和 CRF 对检测轻度圆锥角膜的诊断性能。
在第 1 组与第 2 组中，SE 值（平均值±标准差）分别为-3.55±2.87 屈光度（D）与-1.46±3.09 D（P=0）；K-Avg 分别为 45.09±2.24 与 43.24±1.54 D（P=0）；CA 分别为 3.15±1.87 与 1.07±0.83 D（P=0）；CV 分别为 57.3±2.12 与 60.86±3.39 mm3（P=0）；AC 深度分别为 3.19±0.35 与 3.05±0.43 mm（P=0.0416）；CCT 分别为 503±34.15 与 544.71±35.89 μm（P=0）；CH 分别为 8.50±1.36 与 10.17±1.79 mmHg（P=0）；CRF 分别为 7.85±1.49 与 10.13±2.0 mmHg（P=0）。ROC 曲线分析显示，CH（截断值，9.64 mmHg；灵敏度，87%；特异性，65%；试验准确性，74.83%）和 CRF（截断值，9.60 mmHg；灵敏度，90.5%；特异性，66%；试验准确性，76.97%）总体预测准确性较低，用于检测轻度圆锥角膜。
与对照组相比，轻度圆锥角膜患者的 CH、CRF、CV 和 CCT 值统计学上较低，SE、K-Avg、CA 和 AC 深度值统计学上较高。CH 和 CRF 区分轻度圆锥角膜与正常角膜的效果不佳。
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