The precise effect of argon laser trabeculoplasty on the trabecular meshwork is only partially understood. Its intraocular pressure lowering effect through enhancement of aqueous outflow is well documented. Clinically, this effect seems non-specific for laser characteristics, including wave form, wave length, burn location, clock hours treated, and even to some degree, laser power. The response is delayed in onset, diminishes over time, and in some cases can be renewed with retreatment. Laser photocoagulation of the trabecular meshwork focally destroys, but diffusely stimulates trabecular meshwork cells. Shape alterations in the trabecular meshwork after laser are likely to contribute to outflow enhancement only at very high levels of intraocular pressure. More likely, cellular stimulation activates a molecular biologic chain of events, perhaps within the trabecular extracellular matrix, that permits improved facility of aqueous outflow.