Purpose: The juxtacanalicular tissue (JCT) is the probable site of aqueous outflow resistance in normal eyes and of the increased resistance in primary open-angle glaucoma eyes (POAG). The purpose of this histochemical study was to determine the glycosaminoglycan (GAG) composition and stratification in the JCT of POAG and age-matched normal eyes.
Methods: Five eyes from four normal donors and five eyes from four POAG donors (69 to 80 years of age) were analyzed. Using methods that histochemically preserve GAGs, GAG-degrading enzymes, Alcian blue staining, and real color discrimination to exclude pigment, nuclear staining and unstained areas, the type and amount of GAGs were estimated by compute-raided charge-coupled device color video image analysis. To examine GAG stratification, the JCT was segmented into three regions-anterior, middle, and posterior-to examine regional differences in GAG composition; each region was further divided into four 2-microns layers, from layer 1, adjacent to and including the endothelium of Schlemm's canal, to layer 4, to the first trabecular lamellae.
Results: The normal GAG JCT profile was as follows: hyaluronic acid (HA), 7.78 +/- 1.23 femtograms (fg)/micron2; chondroitin sulfates (CS), 8.18 +/- 0.82 fg/micron2; dermatan sulfate, 0.29 +/- 0.18 fg/micron2; the total, 18.73 +/- 0.68 fg/micron2. In contrast, the POAG GAG JCT profile was as follows: HA 0.57 +/- 0.31 fg/micron2 (P < 0.00001), a 93% decrease; CS 13.49 +/- 0.74 fg/micron2 (P < 0.0001), a 83% increase; dermatan sulfate, 0.90 +/- 0.53 fg/micron2; and the total, 17.31 +/- 0.95 fg/micron2, an 8.2% decrease. The HA was depleted in all layers of all regions of POAG JCT.
Conclusions: Results indicate that the normal JCT is stratified, with HA as the predominant GAG in layers 1 and 2. The POAG JCT is depleted of HA and has an accumulation of CS, which may increase outflow resistance and, consequently, increase intraocular pressure in patients with POAG.