Morphology of the trabecular meshwork within monkey (Macaca speciosa) eyes after irradiation with the free-running Nd:YAG laser.

The long-term tissue response of monkey eyes to trabeculoplasty produced at the chamber angle by neodymium:YAG (Nd:YAG) laser (thermal mode) was investigated. Four weeks after irradiation, a monolayer of corneal-like endothelial cells extended over the trabeculum in impact zones, with partial occlusion of intertrabecular spaces; this condition persisted at all subsequent stages of observation (viz, up to 13 weeks). Both primary and secondary degeneration of trabecular endothelial cells occurred predominantly at the posterior border of the juxtacanalicular tissue, and continued throughout the observation period. Lysis and degradation of collagen fibrils were also prominent in this region, and collagen-phagocytosing cells could be seen at all stages. Although activated fibroblasts were marked in this zone, regeneration processes were, in general, less marked than those of degeneration. The significance of these findings in relation to the mechanism by which trabeculoplasty works is discussed.