Background:The fine structure of the connective tissue constituents of the transition from the sclera to the corneoscleral trabeculum was studied with transmission electron microscopy in open-angle glaucoma.
Material/Methods: 29 cases were investigated. The age of the patients ranged between 50 and 85 years, the glaucoma has lasted from 2 to 30 years. The specimens were taken during trabeculectomy after previous local drug treatment and/or laser and surgical interventions. The normal material derived from eyes enucleated because of intraocular tumours, without intraocular pressure elevation.The specimens were investigated with transmission electron microscopy.
Results: The irregular scleral fibre system gradually arranged into bundles. The bundles were getting finer and finer, and next mixed with the tissue elements of the cornea, chiefly with those of Descemet's membrane. Then the characteristic fourlayered structure of the trabecular bundles developed. These considerable tissue changes were obviously the morphologic basis of the peculiar function of the trabecular meshwork. In the sclera essential pathologic changes could not be demonstrated during the progression of the disease. In the transitional area, however, according to the change of the tissue structure, the quantity of the pathologic alterations gradually increased. In the fully developed trabecular bundles all the pathologic alterations already known in open-angle glaucoma could be detected. This tendency to develop alterations, however, could be recognized in other types of glaucoma, too.
Conclusions: The data on the alterations in the transitional zone from the sclera to the corneoscleral trabeculum may add further information on the sequence of the development of alterations of the morphologic changes found in open-angle glaucoma. These may be similar in morphologic features to those found as age-related changes.

Keywords: Sclera, corneoscleral trabeculum, fine structure of transition, open-angle glaucoma, transmission electron microscopy