Three-dimensional confocal laser microscopy of fibronectin in normal and glaucomatous eyes

Abstract

Aqueous humor exits the anterior chamber of the eye through the trabecular meshwork into Schlemm's canal, a vessel which drains into the systemic circulatory system. The aqueous humor crosses the endothelial lining of Schlemm's canal by means of focal invaginations which form pores and allow digress of fluid into the canal. The trabecular meshwork provides a resistance to fluid flow resulting in a physiologic intraocular pressure in normal eyes. The region adjacent to Schlemm's canal appears to be the site of highest resistance to fluid flow in both normal and glaucomatous eyes. In eyes with primary open angle glaucoma (POAG) the resistance to fluid flow through the trabecular meshwork is abnormally high, causing an elevated intraocular pressure (IOP), which can lead to irreversible damage of the optic nerve and blindness. A definitive morphologic correlate of this disease has not been discovered. Immunohistochemical studies localizing fibronectin in unfixed frozen sections of human eyes have shown elevated levels of fibronectin in the eyes with glaucoma, however the specific distribution of this protein has not been determined due to poor tissue preservation.