Department of Mechanics, Materials Science and Engineering, Wrocław University of Science and Technology, Wrocław, Poland.
Department of Surgery, Wrocław University of Environmental and Life Sciences, Wrocław, Poland.
PLoS One. 2020 Feb 13;15(2):e0228920. doi: 10.1371/journal.pone.0228920. eCollection 2020.
The purpose of this study was to ascertain the relationships between the amplitude of the corneal pulse (CP) signal and the parameters of corneal biomechanics during ex-vivo intraocular pressure (IOP) elevation experiments on porcine eyes with artificially induced ocular pulse cycles. Two experiments were carried out using porcine eyes. In the first one, a selected eye globe was subjected to three IOP levels (15, 30 and 45 mmHg), where changes in physical ocular pulse amplitude were controlled by infusion/withdrawal volumes (ΔV). In the second experiment, six eyes were subjected to IOP from 15 mmHg to 45 mmHg in steps of 5 mmHg with a constant ΔV, where corneal deformation parameters were measured using Corvis ST. In both experiments, at each IOP, the CP and IOP signals were acquired synchronically using a non-contact ultrasonic distance sensor and a pressure transmitter, respectively. Based on the amplitudes of the CP and IOP signals ocular pulse based corneal rigidity index (OPCRI) was calculated. Results indicate positive correlations between ΔV and the physical ocular pulse amplitude, and between ΔV and the corneal pulse amplitude (both p < 0.001). OPCRI was found to increase with elevated IOP. Furthermore, IOP statistically significantly differentiated changes in OPCRI, the amplitudes of CP and IOP signals and in most of the corneal deformation parameters (p < 0.05). The partial correlation analysis, with IOP as a control variable, revealed a significant correlation between the length of the flattened cornea during the first applanation (A1L) and the corneal pulse amplitude (p = 0.002), and between A1L and OPCRI (p = 0.003). In conclusion, this study proved that natural corneal pulsations, detected with a non-contact ultrasonic technique, reflect pressure-volume dynamics and can potentially be utilized to assess stiffness of the cornea. The proposed new rigidity index could be a simple approach to estimating corneal rigidity.
本研究旨在确定在人工诱导的眼脉冲周期的猪眼离体眼内压（IOP）升高实验中，角膜脉冲（CP）信号幅度与角膜生物力学参数之间的关系。使用猪眼进行了两项实验。在第一项实验中，选择一个眼球，使其经受三个 IOP 水平（15、30 和 45mmHg），通过输注/提取量（ΔV）控制物理眼脉冲幅度的变化。在第二项实验中，六个眼球以 5mmHg 的步长从 15mmHg 升高到 45mmHg，在每个 IOP 下，使用 Corvis ST 测量角膜变形参数，其中角膜变形参数使用 Corvis ST 测量。在这两个实验中，使用非接触式超声距离传感器和压力变送器分别同步获取 CP 和 IOP 信号。基于 CP 和 IOP 信号的幅度，计算出基于眼脉冲的角膜刚性指数（OPCRI）。结果表明，ΔV 与物理眼脉冲幅度之间以及与角膜脉冲幅度之间呈正相关（均 p<0.001）。发现 OPCRI 随着 IOP 的升高而增加。此外，IOP 显著区分了 OPCRI、CP 和 IOP 信号幅度以及大多数角膜变形参数的变化（p<0.05）。偏相关分析，以 IOP 为控制变量，显示在第一次压平期间角膜的扁平长度（A1L）与角膜脉冲幅度之间存在显著相关性（p=0.002），并且 A1L 与 OPCRI 之间存在显著相关性（p=0.003）。总之，本研究证明了使用非接触式超声技术检测到的自然角膜搏动反映了压力-容积动力学，并且可能被用于评估角膜的刚性。提出的新刚性指数可能是一种简单的估计角膜刚性的方法。
