Study On Optic Nerve Head In Monkey Model With Experimental Pressure-induced Optic Nerve Damage

The structure of the optic nerve head has been found to correlate with the superior:inferior predilection for injury in glaucoma. This correlation of lamina cribrosa anatomy with apparent increased susceptibility of the superior and inferior optic disc in human glaucoma suggests strongly that the optic nerve head is a likely site of early injury in glaucoma. Progressive susceptibility is most likely the result of unique features of the glaucomatous process. We believe that the most likely explanation lies in the occurrence of gradual changes at either the optic nerve head, within retina, or both. The present study was initiated to investigate the characteristic changes of HRT parameters and pathology in optic nerve head at different periods, by establishing the monkey model with experimental pressure-induced optic nerve damage. Such study may help us to get a deep insight into the changes in optic nerve head after pressure-induced optic nerve damage.Part one: Optic disc topographic parameters measured in the experimental glaucoma by Confocal scanning laser tomographyThe purpose of this part were to investigate (1)the variability of HRT measurements in normal and experimental glaucoma monkeys, (2) the correlations among HRT parameters, (3)the changes of HRT parameters in experimental glaucoma monkeys, (4) the relationship of HRT parameters to Optic Nerve Fiber Number in experimental glaucoma monkeys.4 normal monkeys and 16 laser-induced glaucoma monkeys were studied. Optic disc topography was measured in vivo with HRT. Coefficient of variance of each parameter was obtained from three measurements. Correlations among the topographic parameters were analyzed. Thedifference of each parameter in normal and experimental glaucoma monkeys was analyzed. Nerve fiber count was compared with each HRT parameter.The results showed that the coefficients of variation for rim area, mean dup depth and maximum cup depth were small both in normal and glaucomatous monkeys. The differences of HRT parameters between normal and glaucomatous monkeys was distinguished. Cup /Disk ratio. Rim area, cup volume, disk volume, MnCD, MxCD and CSM correlate significantly to the optic nerve fiber number.Hence the conclusions are the changes of optic nerve head in experimental glaucoma monkeys are similar to that of glaucoma patients. HRT could be used to evaluate optic nerve damage in glaucoma, and rim area is the best parameter.Part two: Changes of optic nerve head in experimental pressure-induced optic nerve damageThe purposes of this part were to investigate the changes of optic nerve head in experimental glaucoma monkeys.4 normal monkeys and 8 experimental glaucoma monkeys were studied. GFAP and HLA-DR expression in optic nerve head were studied with a monoclonal antibody by immunofluorescene. Double immunolabelling of HLA-DR and CD-68 were studied in the optic nerve head. Transmission electron microscopy was also applied to observe the ultrastructural changes in the optic nerve head.The results showed that axon loss was found in experimental glaucoma monkeys. In different optic nerve damage period, GFAP and HLA-DR expression in optic nerve head increased significantly. Colocalisation of CD68 in HLA-DR microglia was observed in optic nerve head. In addition, the results of transmission electron microscopy showed that there are partial swellings of mitochondria. More activated microglias were observed in optic nerve head.Hence the conclusions are that in all stages of experimental glaucomamonkeys, there are activated astrocytes and microglias in optic nerve head. The function of the microglia was phagocytosis.