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S. Akkerman, C.G. H. Bogaard, F.–W. Goudsmit, J.W. Moerkerken, H.J. Simonsz, F.C. T. van der Helm1, S.J. Picken, S. Schutte; A Model of Mechancial Characteristics of the Fluid–Interface Layer Between Tenon and Sclera . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5063.
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© ARVO (1962-2015); The Authors (2016-present)
The fat immediately behind the eye follows approx. 50% of the eye rotation (Schoemaker et al., ARVO 2004). Presumably, a fluid–interface layer facilitates the required sliding. To incorporate this layer in our Delft Finite–element Model of Orbital Mechanics (Schutte et al., Vision Res., accepted for publ.), we developed and validated a model of the mechanical properties of this layer.
Simulation models (Simulink, MatLab) were made to describe the mechanical characteristics of the fluid–interface layer and the orbital fat immediately behind the eye. The orbital fat was modeled with a Kelvin–Voight element; parameters were adopted from other experiments (Schoemaker et al., ARVO 2004). We tested different Maxwell elements and various linear and non–linear dampers as a model for the fluid layer. The models were evaluated with mechanical post mortem measurements on pig eyes (see accompanying abstract by Goudsmit et al.), where a varying moment was applied by means of a pendulum and a perilimbal suction ring to the eye and the rotation of the eye was measured.
These experimental data were used to fit the parameters of models for the fluid (i.e. dampening coefficients), with an optimization algorithm. After the parameter fit, the model was validated using data from previous human in vivo measurements. For the Kelvin–Voight element used to model the energy loss within the fluid layer and the orbital fat a dampening coefficient of 0,64 mNm·s/rad and a spring stiffness of 16,8 mNm/rad were found.
Our model seems suited for modelling the mechanical characteristics of the fluid–interface layer between Tenon and sclera. Validation of the model for human eyes is necessary before the model can be implemented within the Delft Finite–element Model of Orbital Mechanics.
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