Kling Sabine, Akca Imran B, Chang Ernest W, Scarcelli Giuliano, Bekesi Nandor, Yun Seok-Hyun, Marcos Susana
Instituto de Óptica, Consejo Superior de Investigaciónes Cientificas, Madrid, Spain
Wellman Center for Photomedicine and Harvard Medical School, Massachusetts General Hospital, Boston, MA, USA.
J R Soc Interface. 2014 Dec 6;11(101):20140920. doi: 10.1098/rsif.2014.0920.
Most techniques measuring corneal biomechanics in vivo are biased by side factors. We demonstrate the ability of optical coherence tomographic (OCT) vibrography to determine corneal material parameters, while reducing current prevalent restrictions of other techniques (such as intraocular pressure (IOP) and thickness dependency). Modal analysis was performed in a finite-element (FE) model to study the oscillation response in isolated thin corneal flaps/eye globes and to analyse the dependency of the frequency response function on: corneal elasticity, viscoelasticity, geometry (thickness and curvature), IOP and density. The model was verified experimentally in flaps from three bovine corneas and in two enucleated porcine eyes using sound excitation (100-110 dB) together with a phase-sensitive OCT to measure the frequency response function (range 50-510 Hz). Simulations showed that corneal vibration in flaps is sensitive to both, geometrical and biomechanical parameters, whereas in whole globes it is primarily sensitive to corneal biomechanical parameters only. Calculations based on the natural frequency shift revealed that flaps of the posterior cornea were 0.8 times less stiff than flaps from the anterior cornea and cross-linked corneas were 1.6 times stiffer than virgin corneas. Sensitivity analysis showed that natural vibration frequencies of whole globes were nearly independent from corneal thickness and IOP within the physiological range. OCT vibrography is a promising non-invasive technique to measure corneal elasticity without biases from corneal thickness and IOP.
大多数在体测量角膜生物力学的技术都受到附带因素的影响。我们展示了光学相干断层扫描（OCT）振动成像技术在确定角膜材料参数方面的能力，同时减少了其他技术目前普遍存在的限制（如眼内压（IOP）和厚度依赖性）。在有限元（FE）模型中进行模态分析，以研究孤立的薄角膜瓣/眼球的振荡响应，并分析频率响应函数对以下因素的依赖性：角膜弹性、粘弹性、几何形状（厚度和曲率）、眼内压和密度。使用声激励（100 - 110 dB）结合相敏OCT测量频率响应函数（范围50 - 510 Hz），在来自三只牛角膜的角膜瓣和两只摘除的猪眼中对该模型进行了实验验证。模拟结果表明，角膜瓣中的角膜振动对几何参数和生物力学参数都敏感，而在整个眼球中它仅对角膜生物力学参数敏感。基于固有频率偏移的计算表明，后角膜瓣的硬度比前角膜瓣低0.8倍，交联角膜的硬度比未处理角膜高1.6倍。敏感性分析表明，在生理范围内，整个眼球的固有振动频率几乎与角膜厚度和眼内压无关。OCT振动成像技术是一种很有前景的非侵入性技术，可用于测量角膜弹性，且不受角膜厚度和眼内压的影响。
