Hypotensive effect of pilocarpine after argon laser trabeculoplasty

The exact mechanism of action of argon laser trabeculoplasty (ALT) has only been presumptively proposed. There are two hypotheses of action of ALT: the first is the mechanical theory and the second is centered on the possibility of laser-induced modifications of trabecular cells. The goal of our investigation was to verify if pilocarpine determines a decrease of intraocular pressure mainly by a mechanical stretching of the meshwork; if pilocarpine could lower intraocular pressure after ALT; and thus if the mechanism of action of laser treatment could mainly be attributable to a mechanical strain of the trabecular meshwork. Twenty-one patients affected with primary open angle glaucoma had been recruited for the study. Twenty-one eyes underwent trabeculoplasty. All the patients were followed for 6 months. Statistical analysis of the data revealed that pilocarpine was not able to induce a further decrease of intraocular pressure after trabeculoplasty. Moreover, the maximum decrease of intraocular pressure induced by pilocarpine before laser treatment was not statistically different from the tensional values after ALT. The results of the present investigation suggest that the mechanism of action of trabeculoplasty is probably attributable to a mechanical stretching of the trabecular meshwork and the results show the inefficacy of pilocarpine after laser treatment in the management of glaucomatous patients.