We evaluated the effect of elastase, a proteolytic enzyme, on the endothelial meshwork of cultured human trabecular meshwork using a solid agar method. The tissues were obtained from 3 postmortem eyes, aged 64, 71 and 77 years. Elastase was added to the culture medium for 24 h at a concentration of 1 x 10(-1)-10(-4) mg/ml. The cultured specimens were then processed for transmission electron microscopy. We evaluated the electron micrographs to determine the percent area occupied by the cells and the extracellular materials and by the empty space in the endothelial meshwork using computer-assisted morphometry. A statistically significant decrease in extracellular materials with intact trabecular cells was confirmed 24 h following the administration of elastase at the concentration of 1 x 10(-1)-10(-3) mg/ml.