Pathological And Functional Changes Following Optic Nerve Injury In Adult Cat

Objective: Optic nerve injury may cause to severe visual impairment. The proper management is still controversial, and the prognosis is poor. To dynamic observe the features of pathological and functional changes of optic nerve injury and direct clinical treatment.Methods : 20 health adult cats divided randomly into the normal group , the 1d, 3d, 7d, 14d injury group .The right eye were selected as the experiment eye, and the left eye as the control. Though the orbital cavity and sphenoid sinus, optic nerve pipe was damaged by the injury tool which was made by oursel -ves. And animal models were established .The changes of optic nerve were observed using the light microscope and electron microscope, and the flash visual evoked potential (F-VEP) was recorded in normal and optic nerve injury cats.Results :In comparison with normal control groups, Under light, microscope , the optic nerve fiber showed bulb-like degeneration , and most obvious on the 14th day. Under electron microscopy, On the 1st day, some of axons showed bulb -like degeneration , and some of axons swelled and myelin sheaths were loose . On the 3Rd day, more bulb -like degeneration were seen , and myelin sheaths were loose. On the 7th day , many axons myelin sheath degeneration was exacerbated, the infracted areas enlarged . On the 14th day, the nerve fiber without myelin sheath can be seen. Comparing to the normal, F-VEP showed that the latency extended and the amplitude was depressed of wave P after damage.Conclusion: As an animal model , Cat is practical and benefit for the study of clinical optic nerve injury. To the severe visual impairment, Flash visual evoked potential is a reliable , objective and effective method of showing the change of visual function . Pathology changes show more and more severe following optic nerve injury . At the early stage , the proper management may protect the injury optic nerve from secondary damage.