基于光学相干弹性成像的在体晶状体生物力学和光学特性研究

Crystalline lens is a key part of the eye refractive system. The development of several eye diseases, such as cataract and presbyopia, will cause the changes in viscoelastic and optical properties of the lens. Therefore, precise and rapid in vivo imaging and measurement of the lens optical and biomechanical dimensions is extremely valuable for ophthalmological research and clinical diagnosis. However, to the best of our knowledge, there have been no quantitative methods used in clinic for lens elasticity detection, it may be caused by several special features of the lens, such as the location and the transparency, which makes it challenging to quantitatively assess the biomechanical and optical properties of the lens in vivo. To address these issues, the emphasis of this research is to develop a novel optical coherence elastography (OCE) system on the basis of optical coherence tomography (OCT), to realize high resolution, great sensitivity and noninvasive functional and structural imaging of the lens in vivo. By means of combining ultrasound excitation and phase-sensitivity OCT, we will develop an OCE system to achieve the elasticity distribution of the lens with the detection of strain, modeling and resolving of the inverse problem. The custom-built OCE system will apply to image and measure the lens biomechanical and optical properties in cataract cases, to analyze the relationship and correlation between the changes in the lens elasticity and optical dimensions and the development of cataract. The implementation of this project will provide a new precise method for diagnosis of cataract and stiffiness grading of crystalline lens. We believe this method will be powerful and indispensible in clinical diagnosis and mechanism research of cataract and other crystalline lens diseases in the future.

晶状体是眼球屈光系统的重要组成部分，常发性眼科疾病（如白内障、老视）的发生发展与其弹性和光学特征的改变密切相关。因此，实现精准、快速、有效的晶状体成像与参数测量，对眼科疾病的基础研究和诊断治疗，具有十分重要的临床应用价值。但由于晶状体呈透明层状结构且位于眼球内部，因此很难获得其弹性和光学特性改变的精确数据。而临床常用的诊断技术又多属于定性检测，缺乏客观准确的定量检测手段。针对以上问题，本项目在光学相干层析成像（OCT）技术基础上，拟研制一套光学相干弹性成像（OCE）系统，实现在体、无创、高分辨率、高精度、高灵敏的晶状体弹性和结构成像。通过结合脉冲超声与相敏OCT技术，获取晶状体的应变分布；通过构建物理模型和逆问题求解，精确定量晶状体弹性分布；通过系统的动物实验，建立白内障发展程度与晶状体弹性和光学特性间的相关性评价方法。本项目的实施，可望为临床白内障诊疗和晶状体硬度分级提供精准的检测手段。

晶状体特性的改变与白内障等众多眼科疾病的发生发展密切相关，实现精准的晶状体异常检测，对疾病早期诊疗意义重大。但目前常用的晶状体诊断技术多为定性检查。针对以上问题，本项目在光学相干层析成像（OCT）技术基础上，研制了一套光学相干弹性成像系统，实现了高分辨率晶状体在体成像。该系统的探测灵敏度为98dB和相位稳定度为99mrad。基于得到的晶状体数据，通过对晶状体边缘进行检测分割，实现了对晶状体参数（包括晶状体厚度、前后边界曲率半径和离心率等）的精准测量和晶状体地形图重构，并利用特征提取等方法（包括图像熵、LBP、缝隙值）发现正常晶状体和白内障晶状体存在显著的特征差异（p<0.05，配对t检验），证明了该系统在自动识别检测白内障病变的可行性。本项目的实施可望为临床白内障等晶状体疾病的诊疗提供定量检测结果。但在实际开展时受限于实验仪器对于目标的特异性欠缺，在体弹性成像实验的展开还需要进一步优化和加强，另外还需进一步细化白内障发展程度，以证明该实验系统能实现对白内障的早期诊断。