What can we learn from computational model studies of the eye?

U nderstanding the mechanisms of retinal hemorrhages can lead to a better understanding of the externally applied forces and accelerations necessary to cause retinal hemorrhages in infants. Finite element model analysis is one of many computational tools that biomechanical engineers use to help understand how the structural components of the eye may respond to these types of externally applied loads. Because model predictions of tissue deformations and stresses are influenced by the geometry, anatomy, tissue material properties, tissue– tissue interactions, and applied loads used in the model, one should be aware that inaccuracy of these inputs will yield fallacious outputs, and the results of the computer model will have little or no similarity to a real-life response. Because the material properties and tissue–tissue interactions of pediatric ocular tissues have not been measured or published, it is currently impossible for a finite element model to mimic the response of the pediatric eye. Furthermore, it is unknown what values of retinal and ocular stresses produce injury, so these models cannot be used to predict the occurrence of retinal hemorrhages or other ocular injuries. In these circumstances when biomechanical data are limited, engineers use parametric studies—sets of simulations varying some feature of the model over a relevant range—as an important first step to identify tissue components that strongly influence model predictions. Using adult eye property data in a child-sized eye model as a starting point, Rangarajan and colleagues present a parametric study investigating the effect of vitreous and fat material properties on predictions of retinal stress during cyclic rotations of the eye. The authors report significant differences in retinal stress values and distribution when the stiffness of the vitreous is increased 10-fold and when the tissue–tissue interaction is changed (ie, uniform vitreoretinal adhesion in the fluid model versus vitreoretinal adhesion only at the vitreous base and macula in the solid model). Unfortunately, the authors do not report specific references for each of the material properties used in