[Risk factors for development of argon laser trabeculoplasty failure producing membrane in the chamber angle]

The major cause of ALT failure is membrane formation in the chamber angle. The aim of this retrospective study was to identify possible risk factors.

We studied sections from the surgical specimens from all trabeculectomies at our department within 2 years. We identified 122 eyes with at least one preoperative ALT. In 46 specimens enough trabecular meshwork for morphological analysis was present.

Half of the patients showed a membrane covering the trabecular meshwork. In 14 of 23 eyes we could see this membrane even at low-power magnification (40 x). Various possible risk factors were evaluated, but none showed a significant correlation. When we compared only these eyes with membranes visible at low-power magnification with eyes without, however, we found a significant difference in the number of ALTs (mean +/- SD 2.07 +/- 0.73 vs 1.48 +/- 0.59; P = 0.026) and preoperative intraocular pressure (32.0 +/- 9.7 mmHg vs 26.2 +/- 8.4 mmHg; P = 0.04).

We found no distinct risk factor for membrane formation, but it becomes more frequent with every additional laser treatment.