Rheology of the vitreous gel: Effects of macromolecule organization on the viscoelastic properties

Sharif-Kashani, Pooria; Hubschman, Jean‐Pierre; Sassoon, Daniel J.; Kavehpour, H. Pirouz

doi:10.1016/j.jbiomech.2010.10.002

Cited by 88 publications

(118 citation statements)

References 20 publications

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“…While vitreous is comprised of mostly water ($ 99% by weight), the unique extracellular matrix made up of collagen and hyaluronan significantly contributes to the viscoelastic nature of the vitreous (Filas et al, 2014;Nickerson et al, 2008aNickerson et al, , 2008bSebag and Balazs, 1989;Sharif-Kashani et al, 2011). As the eye ages, the collagen networks begin to break down and pockets of liquid form (Sebag, 1987).…”

Section: Introductionmentioning

confidence: 99%

Age-related changes in dynamic moduli of ovine vitreous

Colter

Williams

Moran

et al. 2015

Journal of the Mechanical Behavior of Biomedical Materials

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Section: Introductionmentioning

confidence: 99%

Age-related changes in dynamic moduli of ovine vitreous

Colter

Williams

Moran

et al. 2015

Journal of the Mechanical Behavior of Biomedical Materials

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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: 65%

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 gel structure of the vitreous body is primarily composed of a hydrated double network of collagen types II, V/XI and IX, and hyaluronic acid [31][32][33]. The viscoelastic properties of the vitreous body [31,34,35] affect its behavior, combining the properties of both a solid and a liquid body. Viscoelasticity is possibly due the mobility of the collagen structure and macromolecules, and also the lightly cross-linked nature of the network [34].…”

Section: Discussionmentioning

confidence: 99%

“…The viscoelastic properties of the vitreous body [31,34,35] affect its behavior, combining the properties of both a solid and a liquid body. Viscoelasticity is possibly due the mobility of the collagen structure and macromolecules, and also the lightly cross-linked nature of the network [34]. Thus, the vitreous body is elastic like a solid and viscous like a liquid.…”

Section: Discussionmentioning

confidence: 99%

Short-Term Intraocular Pressure Rise during Locally Induced Force by Ophthalmologic Surgery Applications

et al. 2018

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Purpose: Surgical or diagnostic procedures are often accompanied by a short-term increase in intraocular pressure (IOP). A short-term increase in IOP can occur during refractive procedures, vitreoretinal surgery, transillumination, photocoagulation, or cryocoagulation. A porcine eye model was chosen (n = 89) to compile comparable study data and to de termine correlations between the force induced and the resulting intraocular pressure while excluding the effect of surgeons. Methods: The IOP was measured in the anterior chamber. IOP changes were induced by applying an external force and measured when using a cannula, trocar, and cryocoagulation (n = 32), and correlations between force and resulting IOP were assessed (n = 57). Results: A correlation was noted between the force induced and the IOP increase, which showed a linear dependency. The insertion of a 29-G cannula caused a mean ΔIOP value of 49.1 ± 2.9 mm Hg and an external force of 0.76 N, and that of a 23-G trocar 344.4 ± 5.9 mm Hg and 6.09 N, respectively. The rise in IOP during a simulated cryocoagulation reached values between 57.3 ± 14.8 mm Hg (cryoprobe tip diameter: 0.9 mm) and 130.3 ± 2.9 mm Hg (cryoprobe tip diameter: 7.0 mm). Conclusion: The values of the forces applied can be converted into the resulting IOP based on the specific action. Surgical or diagnostic procedures should, therefore, be evaluated with regard to preexisting pathologies, such as glaucoma.

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Rheology of the vitreous gel: Effects of macromolecule organization on the viscoelastic properties

Cited by 88 publications

References 20 publications

Age-related changes in dynamic moduli of ovine vitreous

Age-related changes in dynamic moduli of ovine vitreous

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

Short-Term Intraocular Pressure Rise during Locally Induced Force by Ophthalmologic Surgery Applications

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