Study Of The Retinal Microvessels And The Effect Of High Intraocular Pressure On Them

The pathological mechanism of glaucoma is still unclear. High intraocular pressure is only one important risk factor, and many studies have demonstrated that the diameters of large vessels around the optic disc grow thinner. How about the retinal microvessels which are more related with the retinal ganglion cells? We focus on this problem.Part One: Comparison of the retinal vessels between normal rhesus monkey and humanPurpose: To compare the differences of the retinal vessels between normal rhesus monkey and human, and provide base for further study about retinal vessels with rhesus monkey as experiment model.Methods: The examination of fudus fluorescent angiography was applied to normal rhesus monkey and human after pupil enlargement. Then the retina of 6 rhesus monkey eyes and 8 human eyecups after corneal transplantation were taken and staind by ADPase method. The distribution, orders and layers of the retinal vessels as well as the perifoveal vascular ring were compared. The results were statistically tested.Results: The Fudus fluorescent angiography images showed that large vessels went through the optic disc and then distributed to the four quadrants of the retina. With ADPase staining distinct retinal vessels were observed from the first order around the optic disc which was the thickest vessels to the fifth order which was called capillaries. The area percentage of the vessels around the optic disc, at the equator and the peripheral respectively had no differences between rhesus monkey and human. There were several vascular layers observed around the optic disc. Only two communicating layers were found at the equtor and only one sparse layer of the capillary was seen at the peripheral retina. The capillaries at the macular area were dense. Intact and irregular perifoveal vascular ring were observed. The differences were not found in area percentage of the vessels and the area, perimeter and diameter of the perifoveal vascular ring between rhesus monkey and human.Conclusions: The retinal vessels in rhesus monkey are quite similar as those in human in the distributions, orders, layers as well as the perifoveal vascular ring. Rhesus monkey is a good animal model for the study of human retinal vessels especially the macular capillaries.Part two: The changes of the macular microvessels in rhesus monkey high intraocular pressure modelPurpose: To make the rhesus monkey intraocular pressure model and investigate the changes of retinal vessels especially macular capillaries under high intraocular pressure.Methods: The intraocular pressures of adult rhesus monkey were increased by laser trabecule cauterized. The eyeballs of the monkeys were execuated. The optic nerves were stained with toluidine blue in semithick slices. The retina was observed under electric microscope and stained by ADPase method. The damage levels of the optic nerve were evaluated by axons count and the pathological appearances of the macular capillaries were also observed. The area, perimeter and diameter of the perifoveal vascular ring and the area percentages of the capillaries were measured and statistically tested.Results: Five mild damage eyes, 3 moderate damage eyes and 3 severe damage eyes in the rhesus monkey high intraocular pressure models were evaluated in this study. Dense and intact perifoveal vascular rings were observed in all the eyes. No obvious changes associated with the damage levels were found. The vessels' area percentages, area, perimeter and diameter of the perifoveal vascular ring were measured and no statistically differences were found. The ultrastructures of the normal capillaries showed regular tubes, good endothelial cells and intact base membranes. While lipoid substances in the capillary tubes, swelling mitochondria in the endothelial cell bodies and uneven base membranes were found in high intraocular pressure eyes.Conclusions: There were no differences in the vessels' area percentage, area, perimeter and diameter of the perifoveal vascular ring found in rhesus monkey high intraocular pressure models compared to normal controls. The ultrastructural changes of the retinal capillary endothelial cells included swelling mitochondria, lipoid substances in the tubes. It was suggested that high intraocular pressure could damage the capillary endothelial cells.Part Three: The preliminary observation of the normal and gluacomatic macular retinal capillaries by adaptive opticsPurpose: To compare the difference in retinal capillaries between normal people and glaucomatic patients by using one high distinguishable method called adptive optics.Methods: Retinal capillaries of normal people and primary open-angle glaucomatic patients over 18 years old were tested by using 37 unit high distinguishable retinal imaging system. The images were taken 1 degree below the foveola. The data were statistically tested.Results: Five clear images in normal group and 4 clear images in primary open-angle glaucomatic group were evaluated. The mean diameter of the capillaries in normal group was 5.39μm, and the mean diameter of the capillaries in the glaucomatic group was 3.91μm which was statistically thinner than that in normal group (P=0.047). No obvious differences in the total length and the number of the vessels were found between the two groups.Conclusions: The macular retinal capillaries in the primary open-angle glaucomatic patients became thinner, which may be an appearance of the vascular automatic dysregulation.