Effect Of High Intraocular Pressure On The Axonal Transport Of Optic Nerve And The Deformation Of Optic Nerve Head

Glaucoma is a group of diseases which is characterized by optic atrophy and visual field defect, and pathological elevated intraocular pressure(IOP) is thought to be the main risk factor. The effects of high IOP on the tissues of eye, especially the damage and compression of optic nerve head(ONH), is one of the reasons for glaucoma blinding. Clinical researches show that the shape of the optic nerve head change before the visual field loss. The change of ONH can lead to the deformation of the Lamina Cribrosa(LC), and thereby compresses the optic nerve axon, which causes the mechanical damage of the optic nerve and the axial flow interruption, and then causes the loss of optic nerve fiber and the death of optic nerve ganglion cells. Therefore, understanding the effect of high intraocular pressure on the axonal transport of optic nerve is very significant in the study of the mechanical mechanism of the optic nerve damage. In this paper, we study the effects of high intraocular pressure on the axonal transport and the deformation of the optic nerve head by establishing animal model of acute high IOP.First, the method of fluorescence labeling was used to study the influences of high IOP on the axonal transport. The acute high IOP of cats was achieved by perfusing saline water into the anterior chamber, and injecting the Rhodamine-β-isothiocyanate(RITC) into the vitreous body of experimental eyes. The control group was set up at the same time. High IOP of the animal model was kept for 6 hours and the metabolism of the retinal ganglion cells was kept for 24 hours. Then the frozen sections of the sagittal plane of the optic nerve were made after the treatment of tissue fixation and dehydration were completed. The axonal transport of the optic nerve for the different intraocular pressure was observed by the laser confocal imaging system. We found that when IOP reached to 50 mmHg(6665 pa) and the axonal transport of the optic nerve was blocked at the lamina cribrosa.Secondly, three-dimensional model of optic nerve of the cat was established under normal IOP. We used confocal laser scanning imaging system to scan frozen slices of the sagittal plane of the cat eye with normal intraocular pressure, and got the sequence images of the optic nerve at the lamina cribrosa. The three-dimensional model of the optic nerve has been established, which can be used to study the mechanism of optic nerve injury.Finally, three-dimensional model of the optic nerve head was established under normal IOP to research the effect of the IOP on the deformation of ONH. The tomographic images of eye fundus of cat with different IOP were obtained using optical coherence tomography(OCT). We obtained three-dimensional model of the optic nerve head which include the retina, choroid, and lamina cribrosa and carried on the finite element analysis of the model. At the same time, under the different IOP, we measured the thickness changes of retina, choroid, and the lamina cribrosa and compared data with the results of the finite element analysis. It is found that the thickness change trend of the selected monitoring stations of the simulation results in tissue is consistent with the experimental results, which show the model is reasonable.In this paper, we study the effects of high intraocular pressure on the axonal transport and establish three-dimensional model of the optic nerve which can be used to the finite element analysis. And the three-dimensional model of the optic nerve head, which includes the choroid, the retina and the lamina cribrosa, is more complicated than the before one. Therefore, this research could be used to set up the more reasonable model of the optic nerve head containing the optic nerve, as well as the mechanism research of the optic nerve injury of the glaucoma.