Modelling the Human Eye N. Green ARUP, Solihull, UK

Notable Features of Model Based on in vivo patient data Multi-part model Mixed volumetric and surface meshes Automated generation of contact surfaces

Purpose of the Study

Computer models of the human eye were constructed for the purposes of studying interactions with foreign bodies.

Segmentation of 5 structures

FE mesh of eye ball, nerves and muscles

Eye hit by a golf ball

Scan and Segmentation in ScanIP

High resolution in vivo MRI scans of a 29 year old Caucasian female was obtained using both a surface and a head coil on a Philips Gyroscan 1.5 Tesla imager. The following structures were segmented from the 3D data set by a Physician: the globe and optic nerve, the bony orbit, the eyelids and facial soft tissues, the extra-ocular muscles.

Mesh Generation in ⁺ScanFE

A number of finite element models were generated based on the segmented image data. Each structure was meshed with mixed hexahedral and tetrahedral elements. The contact surfaces are particularly robust as the master and slave contact faces are paired - contact structures were exported as volumetric meshes and as surface meshes as required. For this application, the bony orbit was modelled as a rigid structure defined by surface shell elements rather than as a volumetric mesh thereby providing some computational saving.

FE Analysis in LS-DYNA^©

An analysis of a golf ball hitting the eye was carried out to demonstrate the robustness of the model for simulation purposes, as well as to demonstrate the remarkable sophistication of biological models which can now be generated based on in vivo data:

• The golf ball is 42 mm in diameter and weighs 45g. It is modelled as a rigid material, impacting the eye at 10 mph in the Y direction.
• The skin is modelled using the Mooney-Rivlin-Rubber material model. A stress-curve for the skin was obtained from literature.
• The bone is modelled as rigid.
• The globe and fat are both modelled as elastic with the same Young's modulus of 49 MPa.
• There is one single surface contact over the whole model, which acts as a self contact for each part and a contact between all parts.