Long-term timolol and epinephrine in monkeys. II. Morphological alterations in trabecular meshwork and ciliary muscle

Cynomolgus monkeys were treated twice daily in one eye with timolol 180 micrograms or epinephrine 540-600 micrograms for several months. In some regions, timolol induced degeneration of trabecular meshwork endothelium and destruction of the central connective tissue core of the lamellae, leaving a rarified meshwork. In some areas, the lamellae and operculum coalesced and appeared 'glued' together. Increased numbers of subopercular cells were present. In other areas the muscle was pulled inwardly, the intramuscular spaces were widened, the shape of Schlemm's canal was altered, and the trabecular meshwork was densified and collapsed, with accumulation of pigment granules within the endothelial cells. Epinephrine induced anterior displacement of the ciliary muscle with narrowing of the chamber angle. There was no damage or loss of trabecular lamellae or endothelial cells, no increase in subopercular cells, and no accumulation of pigment granules within the trabecular cells. The intertrabecular spaces contained protein and erythrocytes. With both drugs, the changes were distributed unevenly.