Sherwood Joseph M, Boazak Elizabeth M, Feola Andrew J, Parker Kim, Ethier C Ross, Overby Darryl R
Department of Bioengineering, Imperial College London, London, United Kingdom.
Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States.
Front Bioeng Biotechnol. 2019 Oct 25;7:276. doi: 10.3389/fbioe.2019.00276. eCollection 2019.
The pressure-volume relationship of the eye is determined by the biomechanical properties of the corneoscleral shell and is classically characterised by Friedenwald's coefficient of ocular rigidity or, alternatively, by the ocular compliance (OC), defined as dV/dP. OC is important in any situation where the volume (V) or pressure (P) of the eye is perturbed, as occurs during several physiological and pathological processes. However, accurately measuring OC is challenging, particularly in rodents. We measured OC in 24 untreated enucleated eyes from 12 C57BL/6 mice using the iPerfusion system to apply controlled pressure steps, whilst measuring the time-varying flow rate into the eye. Pressure and flow data were analysed by a "Discrete Volume" (integrating the flow trace) and "Step Response" method (fitting an analytical solution to the pressure trace). OC evaluated at 13 mmHg was similar between the two methods (Step Response, 41 [37, 46] vs. Discrete Volume, 42 [37, 48] nl/mmHg; mean [95% CI]), although the Step Response Method yielded tighter confidence bounds on individual eyes. OC was tightly correlated between contralateral eyes ( = 0.75, = 0.0003). Following treatment with the cross-linking agent genipin, OC decreased by 40 [33, 47]% ( = 0.0001; = 6, Step Response Method). Measuring OC provides a powerful tool to assess corneoscleral biomechanics in mice and other species.
眼睛的压力-容积关系由角膜巩膜壳的生物力学特性决定，传统上以弗里登瓦尔德眼硬度系数来表征，或者也可以用定义为dV/dP的眼顺应性（OC）来表征。在眼睛的容积（V）或压力（P）受到扰动的任何情况下，OC都很重要，比如在一些生理和病理过程中就会出现这种情况。然而，准确测量OC具有挑战性，尤其是在啮齿动物中。我们使用iPerfusion系统对12只C57BL/6小鼠的24只未经处理的摘除眼球施加可控的压力阶跃，同时测量流入眼睛的随时间变化的流速，以此来测量OC。通过“离散容积”（对流量曲线进行积分）和“阶跃响应”方法（将解析解拟合到压力曲线上）对压力和流量数据进行分析。两种方法在13 mmHg时评估的OC相似（阶跃响应法为41 [37, 46] nl/mmHg，离散容积法为42 [37, 48] nl/mmHg；均值[95%置信区间]），不过阶跃响应法在单眼上得出的置信区间更窄。对侧眼之间的OC紧密相关（r = 0.75，P = 0.0003）。在用交联剂京尼平处理后，OC降低了40 [33, 47]%（P = 0.0001；n = 6，阶跃响应法）。测量OC为评估小鼠和其他物种的角膜巩膜生物力学提供了一个有力工具。
