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O. Y. Tektas, E. Lutjen-Drecoll; Qualitative and Quantitative Morphological Changes in the Vasculature and Extracellular Matrix of the Optic Nerve Head in Glaucomatous Eyes. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3678.
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To analyze changes in the vasculature and extracellular matrix in the prelaminar and laminar region of the optic nerve (ON) in young and old eyes and in eyes with primary open angle glaucoma (POAG).
Morphology of the ON and its anchoring in the sclera was analyzed light- and electronmicroscopically in 37 controls (20 to 96 years) and 18 eyes with POAG. Number of axons, capillary number, capillary density and thickness of the vascular connective tissue sheath (CTS) were quantified and areas containing capillaries with thick sheaths and thin sheaths were determined. The composition of the sheaths was analyzed immunohistochemically using antibodies against type I, III, IV and VI collagen and elastin.
The branches of the short ciliary arteries enter the ON through an elastic fiber (EL) ring connected to the scleral ELs and the connective tissue of the lamina and the vessels within the ON. In contrast to the scleral ELs the morphology of the EL ring resembles that of the choroid and the fibers are accompanied by astrocytes. The entering vessels show a small CTS. Towards the central retinal vein the capillaries gain a thicker CTS containing type I, III, IV and VI collagen. The thickness of the CTS increases with age but significantly more in POAG. In POAG the area occupied by capillaries with thick CTS is significantly larger than in age matched controls. There was no correlation of these data with axon counts. Number of capillaries and capillary density were not different in POAG and age matched controls.
The colocalisation of astrocytes and ELs of the ring surrounding the ON indicates that this anchoring system of the nerve is formed by astrocytes. The connection of the vessels to this ring seems to protect them from occlusion during backwards movement of the ON. Why only the central capillaries gain a thickened CTS and why the area occupied by such vessels is increased in POAG has to be clarified.
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