Results-There were 18 eyes in each group. Baseline characteristics were similar in both groups. In the SLT group the mean IOP at baseline, 1, 3, and 6 months was 22.8 (SD 3.0), 20.1 (4.6), 19.3 (6.0), and 17.8 (4.8) mm Hg, respectively. In the ALT group, the mean IOP at baseline, 1, 3, and 6 months was 22.5 (3.6), 19.5 (4.7), 19.6 (5.6), and 17.7 (3.3) mm Hg, respectively. There was a greater anterior chamber reaction, 1 hour after SLT v ALT (p< 0.01). Patients with previous failed ALT had a better reduction in IOP with SLT than with repeat ALT (6.8 (2.4) v 3.6 (1.8) mm Hg; p = 0.01).Conclusion-SLT appears to be equivalent to ALT in lowering IOP during the first 6 months after treatment. There is a slightly greater anterior chamber reaction 1 hour after SLT. Patients with previous failed ALT had a significantly greater drop in IOP when treated with SLT v ALT. These results need to be confirmed with a larger sample size. (Br J Ophthalmol 1999;83:718-722) Argon laser trabeculoplasty (ALT) has become the standard method of treatment for medically uncontrolled open angle glaucoma in North America.1 2 It has been in use since 1979 when it was first described by Wise and Witter. 3 Argon laser ( = 488-514 nm) improves the outflow of aqueous by photocoagulation of the trabecular meshwork (TM). A number of theories have been proposed to explain this eVect of ALT on aqueous outflow. The most widely accepted are the mechanical and cellular theories. According to the mechanical theory, ALT causes coagulative damage to the trabecular meshwork, which results in collagen shrinkage and subsequent scarring of the TM. This tightens the meshwork in the area of each burn and reopens the adjacent, untreated intertrabecular spaces.2-4 The cellular theory proposes that in response to coagulative necrosis induced by the laser, there is migration of macrophages, which phagocytose debris and thus clear the TM. DiVerent types of lasers with various wavelengths are being investigated for laser trabeculoplasty. Recently, a Q switched, frequency doubled Nd:YAG laser ( = 532 nm) has been described for use in trabeculoplasty 5-7 (Mark A Latina, presented at AAO Annual Meeting, San Francisco, 1997). In tissue cultures, it has been demonstrated that the low power and short duration of this laser can selectively target pigmented TM cells while sparing adjacent cells and tissues from collateral thermal damage and can thus maintain the architecture of the TM.8 This procedure has thus been termed selective laser trabeculoplasty (SLT).The objective of our study was to compare the eYcacy of SLT and ALT in lowering the intraocular pressure (IOP) in patients with open angle glaucoma in a prospective randomised clinical trial.
Patients and methodsA prospective randomised clinical trial was approved by the research ethics board of Ottawa Hospital. The patients included in this trial were those referred to the glaucoma clinic at the University of Ottawa Eye Institute. Patients were included if they had open angle glaucoma (to increase the generali...
