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Michael Dattilo, Dillon Brown, C Ross Ethier; Experimental measurement of optic nerve sheath material properties. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4580.
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© ARVO (1962-2015); The Authors (2016-present)
Changes in the optic nerve sheath (ONS) have been described in several ophthalmologic disorders, such as idiopathic intracranial hypertension (IIH)1,2 and space-flight associated neuro-ocular syndrome (SANS)3,4. Additionally, ONS traction on the optic nerve (ON) head may play a role in glaucoma pathophysiology5,6. Despite the ONS changes reported in SANS and IIH, and its potential role in glaucoma, ONS biomechanical material properties remain poorly understood, particularly in humans. Knowledge of ONS material properties is required for finite element analysis of ONS biomechanics, and may provide insights into the pathophysiology of IIH, SANS4, and glaucoma.
In preparation for testing human tissue, porcine ONSs (pONSs) were dissected from the ONs and placed in 1X PBS. A cylindrical sample of pONS (1 mm diameter), obtained using a biopsy punch, was placed on a MicroTester platform (CellScale, Ontario, Canada) in a temperature-controlled fluid bath (PBS at 37°C). Samples were pre-loaded with a compressive tare load of 100 uN, allowed to equilibrate, and then subjected to a 6-step stress relaxation protocol (5-30% compressive strain). Data from each step were analyzed independently using poroelastic theory to determine the pONS through-plane compressive modulus, the in-plane tensile modulus, and tissue permeability.
pONS compressive modulus was 1.44 ± 0.77 kPa at 5% compressive strain and increased to 7.58 ± 3.17 kPa at 30% strain (mean ± standard deviation). pONS tensile modulus was 8.83 ± 1.70 kPa at 5 % compression and increased to 107.2 ± 23.8 kPa at 30% compression. pONS permeability was 2.49E-16 ± 2.67E-16 m2 at 5% compression, decreasing to 3.21E-18 ± 2.68E-18 m2 at 30% compression.
The pONS showed increased compressive and tensile moduli and decreased permeability under increasing strain, consistent with properties of a biphasic tissue. We will compare the material properties of pONS to those of other species, specifically non-human primates and humans.
This is a 2020 ARVO Annual Meeting abstract.
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