September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
3D fluid-cavity finite-element model of the sliding and deforming orbital fat, and of the eye sliding in Tenon’s capsule during eye rotation.
Author Affiliations & Notes
  • Johan Karel Schonebaum
    Mechanical Engineering, Delft University of Technology, Delft, Netherlands
  • Albert Eddy Huisjes
    Mechanical Engineering, Delft University of Technology, Delft, Netherlands
  • Justin Alexander Smid
    Mechanical Engineering, Delft University of Technology, Delft, Netherlands
  • Paul Christiaan Schalkwijk
    Mechanical Engineering, Delft University of Technology, Delft, Netherlands
  • Huibert Jan Simonsz
    Erasmus MC, Rotterdam, Netherlands
  • Fred keulen
    Mechanical Engineering, Delft University of Technology, Delft, Netherlands
  • Footnotes
    Commercial Relationships   Johan Schonebaum, None; Albert Eddy Huisjes, None; Justin Smid, None; Paul Schalkwijk, None; Huibert Simonsz, None; Fred keulen, None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 4573. doi:
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      Johan Karel Schonebaum, Albert Eddy Huisjes, Justin Alexander Smid, Paul Christiaan Schalkwijk, Huibert Jan Simonsz, Fred keulen; 3D fluid-cavity finite-element model of the sliding and deforming orbital fat, and of the eye sliding in Tenon’s capsule during eye rotation.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4573.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Previous finite element models of orbital mechanics crashed due to extreme deformation of the orbital fat in eye rotation. We solve these problems by using fluid cavities.

Methods : We used Abaqus v6.14 to model orbital fat as a fluid cavity (a bag filled with a fluid). The walls of the cavity consist of 2D shell elements. The fat was assumed to be incompressible with zero visco-elasticity. The eye, modelled as a rigid ball, was pressed - this force representing the force of 2 rectus muscles - into a bin with one fluid cavity representing the orbital fat. it was assumed that there was no shearing between eye and fluid cavity.
Then we modelled the interface between the sclera and Tenon’s capsule as a double-layered flat fluid cavity (fig 1, top half). We exerted a torque to study the deformation and displacement of the fat during eye rotation. Outcomes were stresses and strains in the cavity walls and translation of the center of the eye.

Results : We used pre-formed cavities to avoid large deformations and stresses that occurred when the eyeball was pressed into a flat surface. In this model a combined force of 0.16 N for medial and lateral rectus muscles moved the eye 0.4 mm into the fat. The fat deformed with smooth parabolic curves around the eyeball. When changing the forces to 0.06 N on the right side and 0.10 N on the left side, an eye rotation of 6.8 degrees was obtained. The center of the eye displaced 0.1-0.5 mm.
Modelling the orbital fat as a single component resulted in too much fat moving with the eye. This decreased when a cilindrical membrane separating intra- from extraconal fat was added (fig 1, bottom half).
It was possible to rotate the eye within Tenon’s capsule with almost no friction by use of a flat fluid cavity.

Conclusions : Stable rotation of the eye results from the combined action of pulling muscles and resulting pressure of the fat behind the eyeball (fig. 2).

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

 

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