| Description |
Head trauma is a major cause of long-term neurological deficits, but children are particularly susceptible to complications as head trauma may hinder neurological development. Abuse is the third most common cause of all head injuries in American children. Retinal hemorrhage is often associated with pediatric abusive head trauma, but it is one of the least understood traumatic injuries. The work in this thesis takes important steps towards understanding the mechanism of retinal hemorrhage by first quantifying morphological features in the complex retinal vasculature, then examining how stress and strain manifests during trauma. Preterm and adult sheep retinas were imaged using confocal microscopy. Vessel length, diameter, angular asymmetry, tortuosity and branching were extracted at three depths. Preterm vessels were shorter than the adults', and generally decreased in length, deeper in the retina. Preterm and adult vessel diameters were relatively similar and did not significantly change with depth. Preterm retinas had more vessel branching than adult retinas in the posterior pole and equatorial regions. Branching increased deeper in the retina. The increased vessel branching and decreased lengths suggest infants will experience greater stress and strain during traumatic loading compared to adults. To assess the effect of morphology on stress and strain in a complex vessel network, we created high-resolution, 3D finite element models. Experimentally obtained iv shaking and fall data were applied to simulate two common traumatic scenarios in infants. Stress and strain data were extracted as a function of depth and distribution differences between adults and children were compared. The contribution of morphology and material properties to the mechanical response were evaluated. The adult model experienced higher stresses and lower strains during shaking compared to preterm. Using adult material properties in the preterm model yielded higher stresses and lower strains, suggesting morphological features of the preterm retina increase strain and reduce stress during traction. The adult model experienced lower stress and strain during the fall simulation. This was due to a larger contribution of the morphology compared to material properties at higher loads. Combined, these studies suggest the preterm retinal vasculature has morphological vulnerabilities that increase stress during loading. |
