Introduction of Two Novel Stiffness Parameters and Interpretation of Air Puff-Induced Biomechanical Deformation Parameters With a Dynamic Scheimpflug Analyzer
Introduction of Two Novel Stiffness Parameters and Interpretation of Air Puff-Induced Biomechanical Deformation Parameters With a Dynamic Scheimpflug Analyzer
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DOI：
10.3928/1081597x-20161221-03
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发表时间：
2017-04-01
影响因子：
2.4
通讯作者：
Ambrosio, Renato, Jr.
中科院分区：
文献类型：
--
作者：
Roberts, Cynthia J.;Mahmoud, Ashraf M.;Ambrosio, Renato, Jr.
目的：探讨两个新的硬度参数及其与动态角膜反应(DCR)参数的关系，并对正常眼和圆锥眼进行比较。方法：硬度参数定义为内压合压(A1)除以角膜位移。刚度参数A1使用未变形的角膜和A1之间的位移，而刚度参数最高凹度(HC)使用从A1到HC期间的最大挠度的位移。利用热线风速仪对Corvis ST(Oculus Optikgerate，Wetzlar，德国)气团的时空分布进行了研究。采用调整后的A1点气压(AdjAP1)和基于有限元模型的眼压生物力学校正算法(adjAP1-biop)进行眼压计算。对180只圆锥角膜患者和482只正常眼进行了DCR参数和僵硬参数之间的线性回归分析。每组158名患者的158只眼的DCR参数与BIOP匹配，并使用t检验进行比较。结果：除峰距外，所有DCR参数在正常眼和圆锥眼之间均有显著差异。圆锥角膜具有较低的硬度参数值、较薄的角膜厚度、较短的压平长度、较大的压平速度绝对值、较早的A1次和较晚的二次压平时间、较大的HC变形幅度和较大的HC偏转幅度以及较小的HC凹曲率半径(较大的凹曲率)。结论：与眼压相近的正常眼相比，圆锥角膜眼对变形的抵抗力较弱。作为潜在的生物标志物，这些刚度参数在未来的生物力学研究中可能是有用的。
PURPOSE: To investigate two new stiffness parameters and their relationships with the dynamic corneal response (DCR) parameters and compare normal and keratoconic eyes.METHODS: Stiffness parameters are defined as Resultant Pressure at inward applanation (A1) divided by corneal displacement. Stiffness parameter A1 uses displacement between the undeformed cornea and A1 and stiffness parameter highest concavity (HC) uses displacement from A1 to maximum deflection during HC. The spatial and temporal profiles of the Corvis ST (Oculus Optikgerate, Wetzlar, Germany) air puff were characterized using hot wire anemometry. An adjusted air pressure impinging on the cornea at A1 (adjAP1) and an algorithm to biomechanically correct intraocular pressure based on finite element modelling (bIOP) were used for Resultant Pressure calculation (adjAP1 - bIOP). Linear regression analyses between DCR parameters and stiffness parameters were performed on a retrospective dataset of 180 keratoconic eyes and 482 normal eyes. DCR parameters from a subset of 158 eyes of 158 patients in each group were matched for bIOP and compared using t tests. A P value of less than.05 was considered statistically significant.RESULTS: All DCR parameters evaluated showed significant differences between normal and keratoconic eyes, except peak distance. Keratoconic eyes had lower stiffness parameter values, thinner pachymetry, shorter applanation lengths, greater absolute values of applanation velocities, earlier A1 times and later second applanation times, greater HC deformation amplitudes and HC deflection amplitudes, and lower HC radius of concave curvature (greater concave curvature). Most DCR parameters showed a significant relationship with both stiffness parameters in both groups.CONCLUSIONS: Keratoconic eyes demonstrated less resistance to deformation than normal eyes with similar IOP. The stiffness parameters may be useful in future biomechanical studies as potential biomarkers.