PURPOSE To assess whether corneal viscous properties are measureable with air-puff applanation in patients. METHODS The study had 312 normal eyes, 107 fellow eyes of patients with keratoconus, and 289 keratoconic eyes. The Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany) deformation data for all eyes were analyzed using two models. First, a standard linear solid model (SLM) assumed the cornea was an elastic material only. Second, a two-compartment Kelvin-Voigt model (KVM) assumed the cornea was a visco-elastic material. Corneal stiffness and viscosity were calculated. Further, the deflection amplitude was phase shifted virtually relative to the air-puff applanation force to assess whether the KVM was capable of detecting corneal viscous properties from air-puff applanation. This was similar in concept to measured viscoelastic deformations in other soft tissues. The hysteresis area was also calculated with deformation (cornea and whole globe) and deflection (cornea only) amplitude. The greater the magnitude of the hysteresis area, the greater was the magnitude of corneal viscosity (µc). RESULTS Both the SLM and KVM reported similar magnitudes of corneal stiffnesses (correlation coefficient > 0.99). However, for a given model, corneal stiffness was significantly different between normal, fellow, and keratoconic eyes (P = .001). From the KVM, the corneal viscosity was different between groups (P = .001) but was small in magnitude (order of 10-9). The deflection hysteresis area was also small in magnitude (order of 10-6). In contrast, the KVM detected significant corneal viscosity only when the deflection amplitude was virtually phase shifted with respect to the air-puff applanation force. CONCLUSIONS No significant corneal viscous response was detected in patients who had air-puff applanation. [J Refract Surg. 2019;35(11):730-736.].

中文翻译：

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无法通过吹气法确定角膜的粘性。

目的评估患者吹气压平是否可测量角膜粘性。方法该研究包括312只正常眼，107只圆锥角膜患者同眼和289只圆锥角膜眼。使用两种模型分析了所有眼睛的Corvis ST（OculusOptikgeräteGmbH，德国韦茨拉尔）。首先，标准线性实体模型（SLM）假定角膜仅是一种弹性材料。其次，两室Kelvin-Voigt模型（KVM）假定角膜是粘弹性材料。计算角膜的硬度和粘度。此外，偏转幅度实际上相对于气嘴压紧力相移，以评估KVM是否能够从气嘴压紧力检测角膜粘性特性。这在概念上类似于在其他软组织中测得的粘弹性变形。还使用变形（角膜和整个球体）和变形（仅角膜）幅度来计算磁滞面积。滞后面积的幅度越大，角膜粘度（μc）的幅度越大。结果SLM和KVM均报告了相似的角膜刚度幅度（相关系数> 0.99）。但是，对于给定的模型，正常，同伴和圆锥形圆锥形眼睛之间的角膜刚度显着不同（P = .001）。从KVM来看，各组之间的角膜粘度不同（P = .001），但幅度较小（10-9的数量级）。偏转滞后区域的大小也较小（10-6的数量级）。相比之下，仅当挠曲幅度相对于吹气压力发生相移时，KVM才检测到明显的角膜粘度。结论在气喘压平患者中未检测到明显的角膜粘性反应。[J Refract Surg。2019; 35（11）：730-736。]。