虹膜膨隆对房水流动影响的数值模拟分析

发布时间：2018-06-15 05:57

本文选题：闭角型青光眼 + 虹膜膨隆　；参考：《新乡医学院》2017年硕士论文

【摘要】：背景原发性闭角型青光眼(Primary angle closure glaucoma,PACG)是由于虹膜组织发生非正常变形而致使前房角被虹膜组织物理性关闭,严重阻碍房水的循环流动,并由此造成房水眼压值升高的典型青光眼疾病。其发病率我国各地区均较高,而且有进一步恶化的趋势。已有研究显示虹膜膨隆对房水循环会产生较大影响,因而深入研究虹膜膨隆对房水循环的影响,对PACG的临床诊断、病情发展以及治疗有重要的指导意义。目前采用实验手段研究虹膜膨隆情况下房水的流动情况存在较多的不便,因而需要寻找合适的方法来研究虹膜膨隆情况下房水流动以及虹膜膨隆与眼压之间的变化关系。目的采用ANSYS-FLUENT软件建立二维人眼前房仿真模型,模拟虹膜膨隆情况下房水从前房到后房的整个流动过程。采用该模型分析三种典型虹膜膨隆情况对眼内压变化的影响并分析其变化原因。相关结果可以为预防、诊断PACG病情以及预测病情发展提供一定理论指导。方法1.在超声生物显微镜扫描结果的基础上采用CAD制图软件构建了以人眼前房为主的二维立位(体)几何模型。通过对已有病人虹膜膨隆图像资料的分析,考虑虹膜膨隆夹角的大小,将虹膜膨隆简化为三种类型。这三类夹角分别对应虹膜的膨隆程度如下:正常夹角(49°),中等宽角(30°),极窄角(10°)。2.将虹膜膨隆几何模型导入有限元分析软件ANSYS14.0中。在模拟过程中认为虹膜,角膜和晶状体为刚性,直接忽略其厚度方向的变形,且不考虑房水流动过程中的变形情况。另外在虹膜膨隆眼球房水的流动过程中,在疾病没有进一步发展时,某一段时间内可以认为眼压值已经趋于稳定。此时虹膜的半径可以认为是定值且厚度变化对房水流动的影响较小,主要的影响因素为虹膜膨隆的半径对前后房体积造成的影响。3.考虑房水入口、出口以及虹膜和晶状体接触附近为房水流动复杂区域,因而对这三部分进行网格加密。将房水,虹膜,晶状体等相关结构的物性参数赋值给网格模型,并设定房水入口及出口流速等相关边界条件。4.利用Fluent求解器迭代求解,整理得到三种虹膜膨隆情况对应的眼内压和温度分布计算结果。根据计算结果分析虹膜膨隆对眼内压的影响。结果1.虹膜膨隆仅仅对虹膜附近的温度场分布有影响,远离虹膜的房水温度场分布基本和正常眼球内部温度分布场一致。计算结果表明虹膜膨隆较为严重时,前后房眼内压的差值急剧上升,但是眼前房温度分布变化依然较小。2.在正常眼球和虹膜膨隆眼球中后房和前房各自的压力场均基本不变,但是前后房的压差值变化较大。由于虹膜膨隆造成了前房缩小,后房扩大;同时考虑房水的流动过程中其流量保持不变,因而在正常眼球瞳孔附近后房房水的流速大于虹膜膨隆眼球中后房房水的流速。3.随着虹膜膨隆程度的增加,即膨隆夹角的减小,前房更加缩小和后房更加扩大,因而虹膜膨隆眼球中前后房房水的压力值随膨隆夹角的减小而增加。结论当虹膜膨隆夹角为30°时,压差值相对于正常眼球值变化不是很大。然而当虹膜膨隆较为严重,膨隆夹角为10°时,压差值极大增加。这说明在虹膜膨隆早期眼压变化较小,然而当虹膜膨隆到一定程度,眼压值迅速增加,如不及时控制眼压,病情会迅速加剧。该研究初步揭示了虹膜膨隆对房水流动的影响,为该类闭角型青光眼病情的临床诊断以及病情的发展提供了理论支撑。
[Abstract]:Background primary angle closure glaucoma (Primary angle closure glaucoma, PACG) is a typical green eye disease caused by abnormal deformation of the iris tissue that causes the anterior chamber angle to be physically closed by the iris tissue, which seriously hinders the circulating flow of aqueous humor, and thus causes an elevated ocular pressure in the aqueous humor. The incidence of the disease is higher in all regions of China. There is a trend of further deterioration. Previous studies have shown that iris swelling will have a great impact on the circulation of aqueous humor. Therefore, it is important to study the effect of iris swelling on the circulation of aqueous humor. It has important guiding significance for the clinical diagnosis, development and treatment of PACG. In the case of more inconveniences, it is necessary to find a suitable method to study the relationship between the flow of aqueous humor in the iris bulging and the relationship between the iris swelling and the intraocular pressure. Objective to establish a two-dimensional human anterior chamber simulation model with ANSYS-FLUENT software to simulate the whole flow process of the former room to the rear room under the condition of iris expansion. Analysis of the effects of three typical iris bulging on intraocular pressure changes and analysis of the causes of changes. The results can provide some theoretical guidance for the prevention, diagnosis of PACG condition and prediction of the development of the disease. Method 1. based on the results of ultrasound biomicroscopy, the CAD mapping software is used to build a two-dimensional room with the anterior chamber. By analyzing the image data of the iris bulging of the patients, the iris bulging is simplified into three types by considering the size of the iris expansion angle. The three types of angles corresponding to the iris expansion are as follows: the normal angle (49), the medium width angle (30 degrees), and the extremely narrow angle (10 degrees).2.. In the finite element analysis software ANSYS14.0, the iris, cornea and lens are considered to be rigid in the simulation process, and the deformation of the thickness direction is ignored directly, and the deformation in the process of aqueous fluid flow is not considered. In addition, intraocular pressure can be considered in a certain period of time when the disease has not been developed step by step in the flow process of the iris bulging eyeball room. At this time, the radius of the iris can be considered as the fixed value and the influence of the thickness change on the flow of the aqueous humor is small. The main influence factor is the effect of the radius of the iris on the volume of the front and rear rooms.3., the entrance of the aqueous humor is considered, the exit and the contact of the iris and the lens are close to the complex area of the aqueous fluid flow, so the three The physical parameters of the related structures such as aqueous humor, iris, lens and other related structures are assigned to the grid model, and the relative boundary conditions of the inlet and exit velocity of the aqueous humor are set by the Fluent solver iterative solution, and the results of the calculation of the intraocular pressure and temperature distribution corresponding to three iris bulging conditions are obtained. The results are divided according to the calculation results. The effect of iris bulging on intraocular pressure. Results 1. iris swelling is only affected by the distribution of temperature field near the iris. The distribution of the temperature field far away from the iris is basically the same as the temperature distribution field in the normal eyeball. The distribution changes are still small.2. in the normal eyeball and the iris bulging eyeball, the pressure field of the posterior chamber and the front room is basically unchanged, but the pressure difference between the front and back rooms varies greatly. As the iris enlargement causes the anterior chamber to shrink and the rear room is enlarged, the flow of the room water remains unchanged in the course of the flow of the aqueous humor, so it is near the normal eye pupil. The velocity of water in the posterior chamber is greater than the flow velocity of the iris in the posterior chamber of the iris, with the increase of the iris swelling, that is, the expansion angle decreases, the front room is narrower and the posterior chamber is more enlarged. Therefore, the pressure value of the anterior chamber water in the iris bulging eyeball increases with the increase of the expansion angle. Conclusion when the iris angle is 30 degrees, the iris expansion angle is 30 degrees. The difference in pressure difference is not very large relative to the normal eyeball value. However, when the iris expansion is more serious and the expansion angle is 10 degrees, the difference of pressure increases greatly. This indicates that the change of intraocular pressure is smaller in the early stage of iris expansion. However, when the iris expands to a certain extent, the value of intraocular pressure increases rapidly, if the intraocular pressure is not controlled in time, the condition will rapidly increase. The initial study of the disease will rapidly increase. It reveals the influence of iris expansion on the flow of aqueous humor, and provides theoretical support for the clinical diagnosis and the development of the disease.
【学位授予单位】：新乡医学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R775

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