Rheological properties of the vitreous and the role of hyaluronic acid

Nickerson, Charles S.; Park, John; Kornfield, Julia A.; Karageozian, Hampar

doi:10.1016/j.jbiomech.2008.04.015

Cited by 127 publications

(141 citation statements)

References 17 publications

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“…These would induce an additional contribution to the traction, which is independent of eye movements. Moreover, according to Nickerson et al (2008), the vitreous body under physiological conditions is subjected to a (small) internal tension. Therefore, our model suggests that the traction exerted by the detached vitreous on the retina during saccadic eye movements, possibly in conjunction with the pulling effect due to vitreous shrinking, is very likely to play a significant role in the pathogenesis of retinal detachment.…”

Section: Discussionmentioning

confidence: 99%

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Traction on the retina induced by saccadic eye movements in the presence of posterior vitreous detachment

Repetto

Tatone

Testa

et al. 2010

Biomech Model Mechanobiol

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Posterior vitreous detachment is a fairly common condition in elderly people. Tractions exerted by the detached vitreous on the retina may result in retinal tears and detachments. We studied how these tractions can arise from saccadic eye movements. Numerical simulations have been performed on a two-dimensional model of the vitreous chamber within a rigid spherical sclera, subjected to prescribed finite-amplitude rotations about a vertical axis. The vitreous chamber was assumed to be split into two regions: one occupied by the detached vitreous, modeled as an elastic viscous solid, and the other occupied by the separated liquefied vitreous, modeled as a Newtonian fluid. At the interface between the two phases, we also considered the presence of the vitreous cortex, modeled as an elastic membrane. We tested several different configurations of the interface. In all cases, we found that eye rotations generate large tractions on the retina close to the attachment points of the membrane. Comparing them, we identified configurations of the vitreous detachment that exhibit higher tractions. We also investigated how the response to saccadic movements depends on some physical parameters, in particular on the rheological properties of the solid phase and the membrane. The numerical simulations show that the generated tractions may be of the same order of magnitude as the adhesive force between the retina and the pigment epithelium. Therefore, the model provides a sound physical justification for the hypothesis that saccadic movements, in the presence of posterior vitreous detachment, could be responsible for high tractions on the retina, which may trigger retinal tear formation.

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Section: Discussionmentioning

confidence: 99%

“…The viscosity μ s of the solid can be determined as a function of G as μ s = G /ω, where ω represents the angular frequency adopted in the experiments (equal to 10 Hz both in the experiments of Nickerson et al 2008 andSwindle et al 2008).…”

Section: Vitreous Rheological Propertiesmentioning

confidence: 99%

Traction on the retina induced by saccadic eye movements in the presence of posterior vitreous detachment

Repetto

Tatone

Testa

et al. 2010

Biomech Model Mechanobiol

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“…In the figures, we report various curves that are obtained using different values for the rheological properties of the vitreous humor, proposed in the literature. [3][4][5] In spite of the large differences of the rheological properties of the vitreous humor provided by the authors, the curves are relatively close to one another. Figure 5a shows that the 12 The emmetropic eye corresponds to the thick curve.…”

Section: Myopic Eyesmentioning

confidence: 63%

“…David et al 19 showed that the maximum amplitude of the wall shear stress grows with the eyeball 3 We use x ¼ 10 rad/s. diameter; however, in that article the shape of the eye was not considered, and, most crucially from the clinical point of view, the relationship between the degree of myopia and the stress on the retina was not quantified.…”

Section: Discussion Myopic Eyesmentioning

confidence: 99%

Shape Change of the Vitreous Chamber Influences Retinal Detachment and Reattachment Processes: Is Mechanical Stress during Eye Rotations a Factor?

Meskauskas

Repetto

Siggers

2012

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. We aim to understand how mechanical causation influences retinal detachment and reattachment processes. In particular, myopes suffer retinal detachment more frequently than emmetropes, and following a retinal detachment, scleral buckling promotes retinal reattachment. We test the hypothesis that stresses arising from saccadic eye rotations are involved in the processes, and that the alteration in the stress due to the change in the vitreous chamber geometry is sufficient to explain the phenomena. METHODS.The vitreous chamber of the eye has an approximately spherical shape and it is filled with vitreous humor. We developed a mathematical model, treating the vitreous chamber in emmetropic and myopic eyes as a spheroid and in eyes subjected to scleral buckling as a sphere with a circumferential indentation. We assume that the eye performs prescribed small-amplitude, periodic, torsional rotations and we solve semi-analytically for the fluid pressure, velocity, and stress distributions. RESULTS.The shape of the vitreous chamber has a large effect on the retinal stress. The vitreous and the retina of a highly myopic eye continuously experience shear stresses significantly higher than those of an emmetropic eye. An eye fitted with a scleral buckle experiences large stress levels localized around the buckle. CONCLUSIONS.Our results provide a mechanical explanation for the more frequent occurrence of posterior vitreous detachment and retinal detachment in myopic eyes. To understand how the stress distribution in a buckled eye facilitates reattachment, an additional model of the details of the reattachment process should be coupled to this model. (Invest Ophthalmol Vis Sci. 2012;53:6271-6281) DOI:10.1167/ iovs.11-9390 R etinal detachment (RD) is defined as a separation of the sensory part of the retina from the underlying retinal pigment epithelium, and often leads to sight loss. The most common type is rhegmatogeneous retinal detachment, in which, following liquefaction of the vitreous humor and the development of a tear in the retina, the subretinal space is filled with liquefied vitreous humor. In healthy young eyes, vitreous humor is a gel with complex mechanical properties, which have been studied experimentally by several authors. [1][2][3][4][5][6] The gel state is maintained by a network of collagen fibrils, which typically degrades with age, resulting in vitreous liquefaction. The mechanisms underlying this process are not fully understood.The incidence of myopia is correlated with an increased risk of RD, reported to be four times higher if the refractive error is between À1 and À3 diopters (D), and up to 10 times higher if the error is more than À3 D. 7 It is also known that both posterior vitreous detachment (PVD) and lattice degeneration, which are risk factors for RD, are more common in myopes. [8][9][10] To our knowledge, the reasons for these findings are not fully understood. Myopia is typically associated with a shape change in the vitreous chamber; in particular, myopic eyes are on average larg...

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“…The vitreous chamber is the largest chamber of the eye, delimited anteriorly by the lens and posteriorly by the retina. It is filled with vitreous humour, which in young healthy subjects can be modelled as a viscoelastic fluid (Lee, Litt & Buchsbaum 1992, 1994Nickerson et al 2008;Swindle, Hamilton & Ravi 2008;Sharif-Kashani et al 2011). A recent review of the state of the art in modelling the flow of vitreous humour is provided by Siggers & Ethier (2012).…”

Section: Introductionmentioning

confidence: 99%

Steady streaming of a viscoelastic fluid within a periodically rotating sphere

2014

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Motivated by understanding mass transport processes occurring in the vitreous chamber of the eye, we consider the steady streaming component of the flow generated in a viscoelastic fluid contained within a hollow, rigid sphere performing small-amplitude, periodic, torsional oscillations about an axis passing through its centre. The problem is solved semi-analytically, assuming that the amplitude of the oscillations is small. The paper extends the work by Repetto et al. (J. Fluid Mech., vol. 608, 2008, pp. 71-80), in which the case of a purely viscous fluid was analysed. However, in reality, in young and healthy subjects, the vitreous humour has complex rheological properties, and so here we model it as a viscoelastic fluid. A similar problem was studied by Nikolakis (Eine Theorie für stationäre Drifterscheinungen viskoelastischer Flüssigkeiten, 1992, VDI). In the present model, the steady streaming flow is governed by four dimensionless parameters. We show that, when we account for the viscoelasticity of the fluid, there is a considerably more complex set of possible flow regimes than was found in the purely viscous case, and the flows can be classified into five qualitatively different types. Whereas there was only one circulation cell in each hemisphere in the viscous case, accounting for viscoelasticity it is possible have either one, two or three circulation cells, with different senses of rotation, depending on the parameter values.

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Rheological properties of the vitreous and the role of hyaluronic acid

Cited by 127 publications

References 17 publications

Traction on the retina induced by saccadic eye movements in the presence of posterior vitreous detachment

Traction on the retina induced by saccadic eye movements in the presence of posterior vitreous detachment

Shape Change of the Vitreous Chamber Influences Retinal Detachment and Reattachment Processes: Is Mechanical Stress during Eye Rotations a Factor?

Steady streaming of a viscoelastic fluid within a periodically rotating sphere

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