Analysis of Histostructural Modifications in the Ocular Surface of Patients With Chronic Glaucoma

Purpose: This study aimed to investigate the histostructural modifications that may happen in the anterior sclera and iris of patients with advanced glaucoma (AG) and non-advanced glaucoma (NAG). Methods: Small fragments of anterior sclera and iris were obtained from glaucoma patients subjected to trabeculectomy and peripheral iridotomy to treat their disease. These tissues were histologically analyzed and compared with control (CTR) sclera and iris, and the general structure, extracellular matrix composition, and vasculature were analyzed. Results: For the human sclera, we found that AG samples showed significantly higher amounts of proteoglycans and significantly lower amounts of collagen fibers, along with alterations of spatial collagen organization, than CTR and NAG samples, whereas no differences were found for the contents of glycosaminoglycans and reticular fibers. Analysis of the iris revealed the presence of a pigmented epithelium, a smooth muscle actin (SMA)-positive muscular layer and a stroma enriched in melanocytes revealed by Melan-A immunohistochemistry. A significant decrease in the stromal thickness and reticular fibers contents was found in AG and NAG as compared to CTR. The average diameter of the iris vasculature was significantly reduced in AG, but not in NAG, and the vessel wall was significantly thicker in AG and NAG iris than CTR iris. Conclusions: These results suggest that important histostructural alterations in the anterior sclera and iris are associated with glaucoma, including extracellular matrix and vascular modifications.