Ultrastructural changes in the lamina cribrosa in experimental monkey glaucoma]

We examined the ultrastructural changes in the lamina cribrosa in monkeys with experimental chronic glaucoma. In normal monkey eyes, the extracellular matrix consists of tightly packed collagen fibers, elastic fibers and less ground substance in the beams, and basement membranes associated with vascular cells and astrocytes in the lamina cribrosa. In the experimental glaucomatous eyes there was a marked destruction of collagenous bundles. The empty spaces were expanded and filled with fine fibrillar materials. There were normal by appearing parts and clearly destroyed parts mixed in the same region. Elastic fibers looked isolated from the collagenous bundles around them. Basement membranes were generally thick, multi-laminated, and bent. In addition, basement membrane-like materials, separated from the cells, were often seen in the laminar beams. The lamina cribrosa in experimental chronic glaucoma showed evidence of both destruction and healing or remodeling. These changes might have a influence to the worse for the tissue characterization of the lamina cribrosa, such as resistence to intraocular pressure changes. In conclusion, this may be a factor related with the progression of glaucomatous optic nerve damage.