Histologic findings after argon laser trabeculoplasty in glaucomatous eyes.

The purpose of the study was to determine histologic findings after successful laser trabeculoplasty in eyes with glaucoma. Previous studies have examined eyes in which laser did not lower intraocular pressure, or examined only the region of the laser burn itself. Nineteen autopsy eyes from 14 donors with either primary open angle or pseudoexfoliative glaucoma that had undergone laser trabeculoplasty during life were studied. Clinical records were used to determine the effect of laser in lowering intraocular pressure (IOP). For comparison, 49 glaucomatous eyes that had not undergone laser, and 55 normal eyes were studied as control eyes. Histologic sections from multiple quadrants of each eye were studied by light microscopy, selecting regions between laser spots when the spots were visible. Meshworks from lasered eyes frequently had regions of an expanded juxtacanalicular region associated with numerous superimposed giant vacuoles partially filling Schlemm's canal. This finding was more common in eyes fixed by posterior chamber perfusion, occurring in 90% (9/10) of lasered eyes, while it was found in only 20% (3/15) of glaucomatous control eyes (p=0.01) and 33% (14/43) of normal eyes (p=0.01). The mean decrease in IOP caused by laser was 34%+/-14%, with mean follow-up time before death of 2.7+/-1.7 years. In eyes fixed by immersion the expanded JCT finding was less common, occurring in 22% (2/9) of lasered eyes, but only 9% (3/34) of glaucomatous control eyes and 8% (1/12) of normal eyes. The mean decrease in IOP in these eyes was 39%+/-10%, with mean follow up of 2.3+/-1.0 years until death. Downgrowth of Descemet's membrane over the meshwork was observed in portions of two of the 19 lasered eyes. In conclusion, laser trabeculoplasty associated with decreased IOP appears to cause a remodeling of the juxtacanalicular region of the meshwork. This may be a dynamic, flow dependent finding, as it was more common in eyes fixed by perfusion. Downgrowth of Descemet's membrane over the meshwork was uncommon.