Trabecular meshwork recovery after phagocytic challenge.

The short and long term response of the trabecular meshwork to a phagocytic challenge and the response of the meshwork to different types of foreign particles was studied by injecting one eye of 25 adult cats with a phagocytic agent (zymosan, blood, or latex microspheres) while the fellow eye received a control solution. Eyes were examined histologically at various intervals from one day to five months after infusion. Active trabecular cell phagocytosis and changes in cell shape were found with all agents. The extent of these changes varied with the agent used. Zymosan caused marked changes and inflammation, with numerous macrophages found throughout the meshwork. Trabecular cell migration and cell loss occurred, although it was often difficult to distinguish macrophages from rounded trabecular cells. The meshwork eventually recovered from this inflammatory insult, as trabecular lamellae became less edematous and once again acquired a lining of trabecular cells. Blood and latex microspheres caused less disruption, with microspheres often found in otherwise normal appearing cells. Trabecular cellularity was quantitated after the blood and the zymosan infusions. No cell loss was observed after the blood infusion, while zymosan-infused eyes had an initial 15% cell loss (p less than .04) when compared with fellow control eyes. This zymosan-associated trabecular cell loss may have been due to phagocytosis, inflammation, or a combination of both. The cell loss had recovered by the end of 150 days (p less than .02), as trabecular cell numbers in experimental eyes became comparable to fellow control eyes.