ABSTRACT
Introduction Argon laser trabeculoplasty (ALT) is a firmly established, well-tolerated procedure used to lower intraocular pressure (IOP) in various types of open-angle glaucoma. Laser treatment of the human trabecular meshwork by puncturing Schlemm’s canal was performed initially by Krasnov in 1973, but the lower IOP he described was short-lived.1 In 1979 Wise and Witter reported that the placement of small, evenly spaced, nonpenetrating argon laser spots consistently lowered IOP in phakic eyes that have open-angle glaucoma.2 Laser trabeculoplasty (LTP) is most frequently performed using the argon laser (ALT), although other types of thermal-effect lasers like the diode laser have proved to be equivalent.The treatment consists in targeting the trabecular meshwork (TM) with laser applications via a goniolens. It lowers the IOP, causing an increased outflow facility. The precise mechanism of action is not established and accepted theories include scarring at the site of the laser impact with subsequent tightening of the trabecular beams around it, activation of endothelial cells, release of endothelin and changes in the extracellular matrix.With optimal patient selection an average 25% IOP decrease from baseline can be expected. Such an effect, however, appears to fade with time, with approximately 50% of the eyes still controlled after 5 years and only 20% after longer follow-up.
