Numerical Simulation Of Aqueous Humor Hydrodynamics In Human Eye With Iris Bombe

Background Primary angle closure glaucoma(PACG)is a class of glaucoma resulted from the abnormal iris configuration and the occurrence of anterior chamber angle by the iris tissue mechanical obstruction,leading to aqueous outflow obstruction and elevated intraocular pressure.Hence,it is important to investigae the effect of iris bombe on the aqueous humor hydrodynamics and this can help understand the pathogenesis of PACG.When the aqueous humor hydrodynamics are discussed by experimental method,many problems would emerge and these problems will disturb the invesitgation the effect of iris bombe on the aqueous humor hydrodynamics.Hence,it is necessary to employ an available method to analysis aqueous humor hydrodynamics under iris bombe and find the relationship between intraocular pressure and iris bombe.Objective A two dimensional model for human eye with iris bombe was developed in the ANSYS-Fluent software to simulate the aqueous humor flowing from anterior chamber to posterior chamber.Adopting this model,the effects of three typical iris bombe on the aqueous humor hydrodynamics were discussed.The relative results can provide some theoretical guidance for the prevention,diagnosis of PACG disease and the prediction its progression.Method1.Based on the results of ultrasound biomicroscopy scanning,the two-dimensional and simplified geometric model mainly for anterior chamber with standing posture was constructed successfully.Based on the study of exiting pictures of iris bombe and according to the angle of iris bombe,the simplified iris bombe was divided into three types.The corresponding angles of iris bombe were list as: nominal angle(49°),middle angle(30°),extreme angle(10°).2.The two-dimensional geometric model imported into finite element software-ANSYS was meshed by ICEM module.The iris,corneal and lens were all setted as analytical rigids during the simulation without their deformations along thickness.And the effect of aqueous humor on the iris was also neglected.In addition,when the disease is not further developed,the intraocular pressure can be considerred as stabilization in a certain period of time.At the same time,the radius of the iris can be considered as a constant value and its thickness has little influence on the flow of the aqueous humor.The main factor should be the influence of the iris bombe on the volumes of the anterior and posterior chambers.3.Because of the complex flow problem of aqueous humor inlet,aqueous humor outlet and the contact between iris and lens,these part must be setted as mesh refinement to increase the accuration during simulation.Then,the properties of aqueous humor,iris,lens and other relative parts were assigned to the model.Meanwhile,the inlet velocity,oulet velocity and other boundary condition were also setted.4.Using the fluent solver to iteratively solve the numerical problem,the results about the intraocular pressure difference and temperature distribution can be obtained.And the effects of iris bombe on the intraocular pressure difference of three angles of iris bombe were discussed.Result1.Iris bombe only affects the temperature field distribution near the iris,and the distribution of the temperature field of the aqueous humor away from the iris agree with that of the normal eye.The results show that the intraocular pressure difference between the anterior chamber and posterior chamber increases sharply when the iris bombe is more serious,while the temperature change of the anterior chamber is still small.2.In the normal and iris bombe eye,the pressure fields of the posterior chamber and the anterior chamber are basically the same,while intraocular pressure difference between the posterior chamber and the anterior chamber changes largerly.Since the anterior chamber becoming smaller resulted from iris bombe and posterior chamber expands,and taking the flow of aqueous humor during its flow keeping constant into account,thus the flow rate of aqueous humor in the vicinity of posterior chamber in the normal eye is greater than that of eye with iris bombe.3.With the iris bombe becoming much serious,the iris angle decreases,the anterior chamber is smaller and the posterior chamber is bigger,thus the intraocular pressure difference between the posterior chamber and the anterior chamber increase as the iris angle decrease.Conclusion When the iris angle is 30°,intraocular pressure difference between the posterior chamber and the anterior chamber changle little compared with that of nomal eye.However,the intraocular pressure difference increase sharply when the iris angle is 10°.This shows that the intraocular pressure difference change little when the iris bombe is not serious,but the intraocular pressure difference rapidly increase when the iris bombe increase to a certain extent.If the intraocular pressure difference is ont controlled timely and effectively,the ill will be rapidly worsen.This simulation can be helpful for investigating the aqueous humor hydrodynamics in human eye with iris bombe and providing support for the clinical diagnosis of the angle closure glaucoma.