Related Experiment Video
Updated: Jul 19, 2026

The Mechanics of (Poro-)Elastic Contractile Actomyosin Networks As a Model System of the Cell Cytoskeleton
Published on: March 10, 2023
Elasticity, viscosity, and deformation of orbital fat
Ivo Schoemaker1, Pepijn P W Hoefnagel, Tom J Mastenbroek
1Department of Biomechanical Engineering, Delft University of Technology, Delft, The Netherlands.
Purpose:
For development of a finite element analysis model of orbital mechanics, it was necessary to determine the material properties of orbital fat and its degree of deformation in eye rotation.
Methods:
Elasticity and viscosity of orbital fat of eight orbits of four calves and two orbits of one rhesus monkey were measured with a parallel-plate rheometer. The degree of deformation of orbital fat was studied in two human subjects by magnetic resonance imaging (MRI) through the optic nerve in seven (first subject) or fourteen positions of gaze from left to right. Bifurcations of veins in the fat were used as markers for displacement of the fat.
Results:
The elastic shear modulus (G') of calf orbital fat was between 250 Pa and 500 Pa, and of monkey orbital fat it was between 500 Pa and 900 Pa. The viscous shear modulus (G'') of calf orbital fat was between 80 Pa and 150 Pa, and for monkey orbital fat it was between 300 Pa and 500 Pa. In the MRI scans, it was found that markers in the fat, 1 to 5 mm posterior to the sclera, rotated with the eye for 36% to 53% of eye rotation; the remainder was accounted for by sliding of the eye within the Tenon capsule and within the orbital fat.
Conclusions:
Elastic and viscous shear moduli of orbital fat are low. Little energy is dissipated in the fat. The required deformation of the fat during eye rotation is limited because the eye slides, to some extent, within the Tenon capsule.
Related Concept Videos
Relation between Poisson's ratio, Modulus of Elasticity and Modulus of Rigidity
Elasticity
The elasticity of an object can be described by a stress-strain curve, which represents the relationship between stress...
Circular Shafts - Elastoplastic Materials
As torque on the...
Strain-Energy Density
In the elastic region of a material, the relationship between the stress and the strain is linear and follows Hooke's Law. The strain energy density in this region...
Strain and Elastic Modulus
Stokes' Law
The expression for the force on a solid spherical object in a fluid is called Stokes' law. Stokes' law is valid only for low Reynolds...

