Jesus Danilo A, Majewska Małgorzata, Krzyżanowska-Berkowska Patrycja, Iskander D Robert
Department of Biomedical Engineering, Wroclaw University of Science & Technology, Wroclaw, Poland.
Department of Ophthalmology, Wroclaw Medical University, Wroclaw, Poland.
PLoS One. 2017 May 4;12(5):e0177180. doi: 10.1371/journal.pone.0177180. eCollection 2017.
Tonometry is widely used as the main screening tool supporting glaucoma diagnosis. Still, its accuracy could be improved if full knowledge about the variation of the corneal biomechanical properties was available. In this study, Optical Coherence Tomography (OCT) speckle statistics are used to infer the organisation of the corneal micro-structure and hence, to analyse its influence on intraocular pressure (IOP) measurements.
Fifty-six subjects were recruited for this prospective study. Macro and micro-structural corneal parameters as well as subject age were considered. Macro-structural analysis included the parameters that are associated with the ocular anatomy, such as central corneal thickness (CCT), corneal radius, axial length, anterior chamber depth and white-to-white corneal diameter. Micro-structural parameters which included OCT speckle statistics were related to the internal organisation of the corneal tissue and its physiological changes during lifetime. The corneal speckle obtained from OCT was modelled with the Generalised Gamma (GG) distribution that is characterised with a scale parameter and two shape parameters.
In macro-structure analysis, only CCT showed a statistically significant correlation with IOP (R2 = 0.25, p<0.001). The scale parameter and the ratio of the shape parameters of GG distribution showed statistically significant correlation with IOP (R2 = 0.19, p<0.001 and R2 = 0.17, p<0.001, respectively). For the studied group, a weak, although significant correlation was found between age and IOP (R2 = 0.053, p = 0.04). Forward stepwise regression showed that CCT and the scale parameter of the Generalised Gamma distribution can be combined in a regression model (R2 = 0.39, p<0.001) to study the role of the corneal structure on IOP.
We show, for the first time, that corneal micro-structure influences the IOP measurements obtained from noncontact tonometry. OCT speckle statistics can be employed to learn about the corneal micro-structure and hence, to further calibrate the IOP measurements.
眼压测量作为支持青光眼诊断的主要筛查工具被广泛应用。然而，如果能全面了解角膜生物力学特性的变化，其准确性仍可提高。在本研究中，光学相干断层扫描（OCT）散斑统计用于推断角膜微结构的组织情况，从而分析其对眼压（IOP）测量的影响。
招募了56名受试者进行这项前瞻性研究。考虑了角膜的宏观和微观结构参数以及受试者年龄。宏观结构分析包括与眼部解剖结构相关的参数，如中央角膜厚度（CCT）、角膜半径、眼轴长度、前房深度和角膜白到白直径。微观结构参数包括OCT散斑统计，与角膜组织的内部组织及其一生中的生理变化有关。从OCT获得的角膜散斑用广义伽马（GG）分布进行建模，该分布由一个尺度参数和两个形状参数表征。
在宏观结构分析中，只有CCT与IOP显示出统计学上的显著相关性（R2 = 0.25，p<0.001）。GG分布的尺度参数和形状参数之比与IOP显示出统计学上的显著相关性（分别为R2 = 0.19，p<0.001和R2 = 0.17，p<0.001）。对于研究组，年龄与IOP之间发现了微弱但显著的相关性（R2 = 0.053，p = 0.04）。向前逐步回归表明，CCT和广义伽马分布的尺度参数可以组合在一个回归模型中（R2 = 0.39，p<0.001），以研究角膜结构对IOP的作用。
我们首次表明，角膜微结构会影响非接触眼压测量获得的IOP值。OCT散斑统计可用于了解角膜微结构，从而进一步校准IOP测量。
