Rheological behaviour of vitreous humour

Abstract

The vitreous humour (VH) is a complex biofluid that occupies a large portion of the eyeball between the lens and the retina, and exhibits non-Newtonian rheological properties that are key for its function in the eye. It is often possible to distinguish two different phases in VH, known as liquid and gel phases (Sebag, 1987). In this work, we present a detailed rheological characterisation of the two phases of the VH under shear and extensional flow conditions. Healthy New Zealand rabbit eyes were used to measure the surface tension and the shear and extensional rheological properties of VH in different phase conformations and at different times after dissection. The results show that VH liquid phase exhibits a surface tension of 47.8 mN/m, a shear thinning behaviour reaching a viscosity plateau around 10-3 Pa.s for shear rates above 1000 s-1, and an average relaxation time of 9.7 ms in extensional flow. Interestingly, both VH phases present higher storage modulus than loss modulus and the measurements performed with VH gel phase 4±1 hours after dissection exhibit the highest moduli values. The compliance measurements for the gel phase show a viscoelastic gel behaviour and that compliance values decrease substantially with time after dissection. Our results show that the two VH phases exhibit viscoelastic behaviour, but with distinct rheological characteristics, consistent with a gel phase mostly composed of collagen entangled by hyaluronan and a second phase mainly composed of hyaluronan in aqueous solution

Macro- and Microscale Properties of the Vitreous Humor to Inform Substitute Design and Intravitreal Biotransport

“…Before Nickerson et al 2005, common techniques used were ultrasound, 39 light scattering, 35,45 periodic oscillations, 43,44 compression chucks, 46 MRI, 42 or microrheology. 20,40 Following the studies by Nickerson et al,- 3,38 there have been at least 10 studies that used shear rheology. Some other rheometric techniques used were capillary rheology, 33,34 cavitation rheology, 32 microrheology, 22 and creep testing.…”

“…Nickerson et al and various other authors have pointed out that the properties of the vitreous rapidly change following dissection, going from a homogeneous vitreous to a heterogeneous gel surrounded by a pool of liquid. 3,17,20,38 This expulsion of liquid from the vitreous humor occurs rapidly, within 10 minutes of dissection. It is likely that the measured properties of the dissected in vitro vitreous samples are different from the properties of intact in vivo vitreous in the eye.…”

Supramolecular Presentation of Hyaluronan onto Model Surfaces for Studying the Behavior of Cancer Stem Cells

“…[7] In vivo, this is a key characteristic which significantly contributes to the viscoelastic properties of several tissues, including cartilage [8] and the vitreous humor. [9] In addition to its biophysical characteristics, HA itself interacts with cells via cell-surface receptors such as CD44 and receptor for hyaluronan-mediated motility (RHAMM). [7] HA is also known to accumulate in the tumor microenvironment and, signalling via these receptors, can support metastasis, cancer cell proliferation, and multidrug resistance.…”

Patterned surface charges coupled with thermal gradients may create giant augmentations of solute dispersion in electro-osmosis of viscoelastic fluids

“…Typical miniaturized devices in the modern day lab-on-a-chip environment handle biological fluids that tend to disobey Newton's law of viscosity [26][27][28][29][30][31]. In particular, biofluids, like blood plasma, saliva, synovial fluid and vitreous humour [32][33][34][35][36], exhibit viscoelasticity under certain straining conditions. Hence, the use of viscoelastic models to predict their dynamical features remains pertinent [37][38][39][40][41][42].…”