Fibronectin, an extracellular glycoprotein, has been shown to be produced by human trabecular cells in culture by our group as well as Polansky and co-investigators. Studies of Rodrigues et al suggested that fibronectin may be one of several glycoproteins found in increased amounts in the corneoscleral trabecular meshwork of glaucomatous eyes. The authors have developed a sensitive immunoassay utilizing avidin-biotinylated enzyme complex (ABC) to detect low levels of fibronectin in frozen sections of human eyes. The authors have used this immunoassay together with a perfusion technique to demonstrate distribution patterns of fibronectin present in human aqueous drainage channels. The authors found that fibronectin is present in larger quantities in the aqueous drainage channels than in the surrounding tissues in 18 eyes from older patients.