| Though the history of Hyperbaric Oxygen (HBO) applied in medicine is very short, its unique curative effect on certain diseases has attracted increasing attention of the medical profession. It is significant to prevent side effects and complications in ensuring the efficacy of hyperbaric oxygen therapy. Optic nerve conducts visual impulses, which is made of sensory fibers. If optic nerve was injured, it would affect the visual function and sometime lead to blindness. As optic nerve injury is irreversible, even after treatment, impaired visual function couldn't recover.It has not been reported in the literature that whether optic nerve is compressed when orbital damaged patient accept hyperbaric oxygen therapy. In this paper, the three-dimensional finite element model of damaged orbital cavity with tissues was developed using some simplifications and reasonable assumptions, and the high pressure situation on the orbital cavity surface was simulated. Combined with the actual situation of the orbital damaged patient, the stresses of optic nerves in both sides of orbital cavity were analyzed. These results can not only regard as mechanical basis for orbital damaged patients before accepting hyperbaric oxygen therapy and to avoid the optic nerve damage during the treatment, but also for the subsequent detailed study.The main work of this research is outlined as the followings:1: On the basis of the CT-scan images of the injured human head, the outlines of tissues were gained by using the MIMICS software (trial version).2: The three-dimensional finite element model was developed using the outlines of tissues in ANSYS. In order to response to the real situations of optic nerve in human body, injured orbital cavity, eyeball, adipose body of orbit as well as brain was included in this model which contained 46189 nodes and 249115 elements. Elastic material model was used to characterize the material feature.3: Combined with the real situation in the hyperbaric oxygen chamber, the stress state of the optic nerve was simulated using ANSYS software.The main conclusions were as follows:1. The maximum stress of the optic nerve both in the injured part and the intact part of orbital cavity occurred in the contact part of the optic nerve and eyeball. This result is consistent with the conclusion that optic nerve is compressed as the intraocular pressure rising. 2. Skull can effectively protect optic nerve from the external forces. When the external pressure is constant, as we assumed that the elastic modulus of skull in the injured part of orbital cavity was reduced, the stress of optic nerve in the injured part of orbital cavity increased gradually.3. When the elastic modulus of skull is constant, as the external pressure increasing, the maximum stress of optic nerve increased sharply. It is showed that optic nerve may be compressed during hyperbaric oxygen therapy.4. The stress of optic nerve in the injured part of orbital cavity is far greater than the stress of optic nerve in the intact part of orbital cavity. |
