猫视乳头三维模型重建及有限元分析

Three-dimensional reconstruction and finite element analysis of the optic nerve head of a cat

背景:青光眼是一种以视野缺失为特征的不可逆性致盲眼疾病,临床研究表明,眼底视乳头组织早在视野缺失前已经发生了变化,而且视乳头中各组织的形态变化已经成为目前青光眼早期诊断以及确定病情发展的关键参考点,因此研究高眼压下视乳头各组织的形态变化具有重要的意义。目的:建立包含筛板、视网膜和脉络膜的视乳头组织三维模型,分析急性高眼压下视乳头各组织的厚度变化。方法:1选择健康家猫,排除屈光介质不清等各种眼疾,利用深度增强的频域相干光断层扫描成像技术获得猫在正常眼压下眼底视乳头组织的断层序列图。2分别获得视网膜、脉络膜和筛板的三维结构模型,并组装视乳头三维模型。利用有限元方法分析不同眼压下视网膜、脉络膜和筛板的厚度变化。3通过前房灌注的方法制造急性高眼压动物模型,利用深度增强的频域相干光断层扫描成像技术获得猫眼在不同眼压下的断层序列图。测量不同眼压下脉络膜、视网膜和筛板的厚度变化,并与有限元计算结果进行比较。结果与结论:随着眼压的逐渐升高,脉络膜、视网膜和筛板呈变薄趋势,视乳头的杯盘比逐渐变大。而关于脉络膜、视网膜和筛板的厚度变化,测量结果与有限元计算的结果趋势程度相一致,因此利用光学相干断层扫描仪获得的断层序列图对眼底各组织进行三维重建来分析高眼压下眼底各组织的形态变化可行,用有限元分析的方法可以对眼底各组织在高眼压下的形态变化进行预测,这对确定青光眼的病程发展有一定的指导意义。

BACKGROUND： Glaucoma is a kind of eye disease that can cause irreversible blindness which is characterized by visual field loss. Clinical research shows that the optic nerve head has changed before the visual field loss. The morphological changes of the optic nerve head have become the key to determine the early diagnosis of glaucoma and disease development. So it has important significance for us to study the morphological changes of the tissues of optic nerve head under the high intraocular pressure. OBJECTIVE： To establish three-dimensional finite element model of optic nerve head which includes choroid, retina and lamina cribrosa, and analyze the thickness of the optic nerve head under the acute high intraocular pressure. METHODS： （1） We chose healthy cats without refractive media and other eye diseases. The tomographic sequence images of the optic nerve head of a cat were obtained with the intraocular pressure of the normal value by using enhanced depth imaging spectral-domain optical coherence tomography. （2） The three-dimensional model of the retina, choroid and lamina cribrosa was obtained. Three-dimensional model of optic nerve head was established by assembling the model of the retina, the choroid and the lamina cribrosa. The thickness of the retina, choroid and lamina cribrosa was analyzed under different intraocular pressures by using the method of finite element analysis. （3） Animal model of acute ocular hypertension was established by methods of anterior chamber perfusion. The tomographic sequence images of the optic nerve head of a cat were obtained with different intraocular pressures by using enhanced depth imaging spectral-domain optical coherence tomography. Then, we measured the thickness changes of the choroid, retina and lamina cribrosa under different intraocular pressures, and compared with the results of finite element analysis. RESULTS AND CONCLUSION： The thickness of the choroid, retina and lamina cribrosa trended to be thin, and the cup dish ratio of optic nerve head increased gradual y with the increased intraocular pressures. Regarding to the thickness changes of the choroid, retina and lamina cribrosa, the trend of experimental measurement results was consistent with finite element calculation results. Hence, it is feasible to analyze morphological changes of every fundus tissue under high intraocular pressure using the tomographic sequence images obtained by optical coherence tomography. We can predict the morphological changes of the optic nerve head tissue by finite element analysis, which has certain guiding significance in determining the progression of glaucoma.