Abstract
Purpose :
Abusive head trauma (AHT) is a leading cause of death and disability in children. Retinal hemorrhage (RH) is a sign which helps physicians to make the correct decision of the possibility of AHT. However, in some cases retinal hemorrhage is caused by accidental trauma. Therefore, distinguishing the pattern of retinal hemorrhage caused by AHT or accidental trauma is crucial. The main aim of this research is to simulate eyeball movement during baby shaking to find out stress distribution pattern on the posterior pole of the eyeball, caused by AHT, which is aligned with the pattern of blood spots in that region and then correlate that with clinical findings.
Methods :
3D finite element model of an infant eye was generated which consists of vitreous, retina and sclera layers, The material properties of the components were extracted from the previous experimental works. A fundus photograph was employed to find the exact location of attached retinal vessels. A dynamic analysis was then conducted to simulate translational and rotational movements of the eyeball and to record the variation of induced stresses on the posterior pole of the eyeball.
Results :
Calculated Mises stress was observed at the attached vessels’ locations and high stress concentration was observed at the bifurcation locations. It is worthy to mention that at the time point of 0.2181 s where shaking induces the maximum value of acceleration, the eyeball undergoes a severe rotational movement. This point clarifies the effect of rotation in the course of baby shaking on formation of retinal hemorrhage. Moreover, it was observed that the stress values are approximately constant through the thickness of the retina.
Conclusions :
Stress distribution pattern during shaking revealed that attached vessels at the all regions of bifurcations experience higher stresses which means higher possibility of blood spot formation. However, there is a significant difference of stresses for the all attached vessels compared with the regions without attachment. This finding are consistent with the clinical findings of the location of RH. In addition, according to clinical observations of AHT, retinal hemorrhage usually occurs in all three layers of retina which was confirmed by our finite element results.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.