Physiology of aqueous humor dynamic in the anterior chamber due to rapid eye movement

Modarreszadeh, Amir; Abouali, Omid; Ghaffarieh, Alireza; Ahmadi, Goodarz

doi:10.1016/j.physbeh.2014.05.017

Cited by 14 publications

(15 citation statements)

References 28 publications

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“…Therefore, under the rapid eye movement, the study of the mixing aqueous humor in the anterior chamber becomes more meaningful. Modarreszadeh [25] carried out a detailed simulation study on this issue. The importance of the driving mechanism for aqueous flows was considered in our study.…”

Section: Discussionmentioning

confidence: 99%

Fluid and structure coupling analysis of the interaction between aqueous humor and iris

et al. 2016

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BackgroundGlaucoma is the primary cause of irreversible blindness worldwide associated with high intraocular pressure (IOP). Elevated intraocular pressure will affect the normal aqueous humor outflow, resulting in deformation of iris. However, the deformation ability of iris is closely related to its material properties. Meanwhile, the passive deformation of the iris aggravates the pupillary block and angle closure. The nature of the interaction mechanism of iris deformation and aqueous humor fluid flow has not been fully understood and has been somewhat a controversial issue. The purpose here was to study the effect of IOP, localization, and temperature on the flow of the aqueous humor and the deformation of iris interacted by aqueous humor fluid flow.MethodsBased on mechanisms of aqueous physiology and fluid dynamics, 3D model of anterior chamber (AC) was constructed with the human anatomical parameters as a reference. A 3D idealized standard geometry of anterior segment of human eye was performed. Enlarge the size of the idealization geometry model 5 times to create a simulation device by using 3D printing technology. In this paper, particle image velocimetry technology is applied to measure the characteristic of fluid outflow in different inlet velocity based on the device. Numerically calculations were made by using ANSYS 14.0 Finite Element Analysis. Compare of the velocity distributions to confirm the validity of the model. The fluid structure interaction (FSI) analysis was carried out in the valid geometry model to study the aqueous flow and iris change.ResultsIn this paper, the validity of the model is verified through computation and comparison. The results indicated that changes of gravity direction of model significantly affected the fluid dynamics parameters and the temperature distribution in anterior chamber. Increased pressure and the vertical position increase the velocity of the aqueous humor fluid flow, with the value increased of 0.015 and 0.035 mm/s. The results act on the iris showed that, gravity direction from horizontal to vertical decrease the equivalent stress in the normal IOP model, while almost invariably in the high IOP model. With the increased of the iris elasticity modulus, the equivalent strain and the total deformation of iris is decreased. The maximal value of equivalent strain of iris in high IOP model is higher than that of in normal IOP model. The maximum deformation of iris is lower in the high IOP model than in the normal IOP model.ConclusionThe valid model of idealization geometry of human eye could be helpful to study the relationship between localization, iris deformation and IOP. So far the FSI analysis was carried out in that idealization geometry model of anterior segment to study aqueous flow and iris change.

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Section: Discussionmentioning

confidence: 99%

Fluid and structure coupling analysis of the interaction between aqueous humor and iris

et al. 2016

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“…REM is a normal feature of a particular phase of sleep, and consists of repeated side-to-side rotations that can have a wide range of amplitudes (Takahashi & Atsumi 1997). For our model we adopt the same parameters as Modarreszadeh et al (2014) and consider two cases: (i) 'average REM' with β = 6.27 deg and ω f = 58.73 deg/s, corresponding to the average of the experimental data by Takahashi & Atsumi (1997), and (ii) 'maximum amplitude REM' with β = 61.5 deg and ω f = 491.98 deg/s, which is the highest amplitude reported in the measurements, and these points are also reported in figure 3.…”

Section: Eye Rotationsmentioning

confidence: 99%

“…Various mechanisms produce fluid flow in the AC of the eye, which have been fairly well studied from the mechanical point of view. The main mechanisms include: (i) aqueous secretion and drainage (Friedland 1978;Silver & Quigley 2004;Fitt & Gonzalez 2006;Villamarin et al 2012;Repetto et al 2015;Dvoriashyna et al 2017); (ii) flow driven by buoyancy effects due to a temperature gradient across the AC (Canning et al 2002;Heys & Barocas 2002;Fitt & Gonzalez 2006;Villamarin et al 2012;Repetto et al 2015); (iii) eye rotations (Abouali et al 2012;Modarreszadeh et al 2014;Repetto et al 2015;Boushehrian et al 2016); and (iv) Flow due to deformation of the shape of the anterior chamber, such as occurs during lens accommodation, accidents or if the eye is rubbed. Repetto et al (2015) showed that, of the first three mechanisms listed in the previous paragraph, rotations of the eye produce the most intense flow in the AC, and thus contribute to the majority of the wall shear stress on the cornea.…”

Section: Introductionmentioning

confidence: 99%

“…Movements of the eye are routine and take a variety of different forms. Some rotations are close to periodic oscillations, and approximating them as a pure frequency oscillation has been a popular simplification in the literature, both in experimental works (Repetto et al 2005;Bonfiglio et al 2013Bonfiglio et al , 2015 and theoretical works (David et al 1998;Repetto et al 2010;Abouali et al 2012;Modarreszadeh et al 2014). In this work we also make use of this assumption.…”

Section: Introductionmentioning

confidence: 99%

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Oscillatory and steady streaming flow in the anterior chamber of the moving eye

2019

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We study the flow induced by eye rotations in the anterior chamber (AC) of the eye, the region between the cornea and the iris. We model the geometry of the AC as a thin domain sitting on the surface of a sphere, and study both the simpler case of a constant-height domain as well as a more realistic AC shape. We model eye rotations as harmonic in time with prescribed frequency $\unicode[STIX]{x1D714}_{f}$ and amplitude $\unicode[STIX]{x1D6FD}$, and use lubrication theory to simplify the governing equations. We write the equations in a reference frame moving with the domain and show that fluid motion is governed by three dimensionless parameters: the aspect ratio $\unicode[STIX]{x1D716}$ of the AC, the angular amplitude $\unicode[STIX]{x1D6FD}$ and the Womersley number $\unicode[STIX]{x1D6FC}$. We simplify the equations under the physiologically realistic assumptions that $\unicode[STIX]{x1D716}$ is small and $\unicode[STIX]{x1D6FC}$ large, leading to a linear system that can be decomposed into three harmonics: a dominant frequency component, with frequency $\unicode[STIX]{x1D714}_{f}$, and a steady streaming component and a third component with frequency $2\unicode[STIX]{x1D714}_{f}$. We solve the problem analytically for the constant-height domain and numerically as the solution of ordinary differential equations in the more realistic geometry. Both the primary flow and the steady streaming are shown to have a highly three-dimensional structure, which has not been highlighted in previous numerical works. We show that the steady streaming is particularly relevant from the clinical point of view, as it induces fluid mixing in the AC. Furthermore, the steady flow component is the dominant mixing mechanism during the night, when the thermal flow induced by temperature variations across the AC is suppressed.

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“…We hypothesized that human CECs may be physiologically armed with self-protective mechanisms against aging and injury, including surgery, trauma, and the lifelong shear stress of aqueous flow in corneal endothelium generated by rapid eye movements during sleep 38 and convection flow in the anterior chamber. To explore this hypothesis, we investigated the expression of RNase 5, a candidate homeostatic factor, in normal and decompensated human corneal endothelial tissue.…”

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confidence: 99%

Ribonuclease 5 facilitates corneal endothelial wound healing via activation of PI3-kinase/Akt pathway

Kim

Park

Lee

et al. 2016

Sci Rep

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To maintain corneal transparency, corneal endothelial cells (CECs) exert a pump function against aqueous inflow. However, human CECs are arrested in the G1-phase and non-proliferative in vivo. Thus, treatment of corneal endothelial decompensation is limited to corneal transplantation, and grafts are vulnerable to immune rejection. Here, we show that ribonuclease (RNase) 5 is more highly expressed in normal human CECs compared to decompensated tissues. Furthermore, RNase 5 up-regulated survival of CECs and accelerated corneal endothelial wound healing in an in vitro wound of human CECs and an in vivo cryo-damaged rabbit model. RNase 5 treatment rapidly induced accumulation of cytoplasmic RNase 5 into the nucleus, and activated PI3-kinase/Akt pathway in human CECs. Moreover, inhibition of nuclear translocation of RNase 5 using neomycin reversed RNase 5-induced Akt activation. As a potential strategy for proliferation enhancement, RNase 5 increased the population of 5-bromo-2′-deoxyuridine (BrdU)-incorporated proliferating CECs with concomitant PI3-kinase/Akt activation, especially in CECs deprived of contact-inhibition. Specifically, RNase 5 suppressed p27 and up-regulated cyclin D1, D3, and E by activating PI3-kinase/Akt in CECs to initiate cell cycle progression. Together, our data indicate that RNase 5 facilitates corneal endothelial wound healing, and identify RNase 5 as a novel target for therapeutic exploitation.

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Physiology of aqueous humor dynamic in the anterior chamber due to rapid eye movement

Cited by 14 publications

References 28 publications

Fluid and structure coupling analysis of the interaction between aqueous humor and iris

Fluid and structure coupling analysis of the interaction between aqueous humor and iris

Oscillatory and steady streaming flow in the anterior chamber of the moving eye

Ribonuclease 5 facilitates corneal endothelial wound healing via activation of PI3-kinase/Akt pathway

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