Effects of Er:YAG laser trabecular ablation on outflow facility in cadaver porcine eyes.

Abstract

Mid-infrared laser technology opens new perspectives in experimental glaucoma surgery. The aim of this study was to establish the effectiveness of Er:YAG laser photoablation of the trabecular meshwork in increasing outflow facility in cadaver porcine eyes. Eye cups of 20 freshly enucleated cadaver porcine eyes were fixed in an anterior segment perfusion system, measuring outflow facility under constant pressure conditions (7-13 mmHg) over a period of 45 min. Trabecular ablation was performed using a pulsed Er:YAG (2.94 microns) laser. Radiation was delivered in a single 4-mJ pulse of 200 microseconds duration by means of an articulated zirconium fluoride optical fibre and a 320-microns quartz-fibre tip. Er:YAG laser treatment yielded reproducible ablation areas confined to the trabecular meshwork, with a diameter corresponding to that of the fibre tip. Collateral thermal damage extended up to a depth of 30 microns. Outflow facility measurements revealed an increase (mean +/- SD) from 0.128 +/- 0.041 microliter min-1 mmHg-1 in control eyes (n = 11) to 0.308 +/- 0.093 microliter min-1 mmHg-1 in treated ones (n = 9). Application of the photoablative Er:YAG laser technique in non-fistulating trabecular surgery produces patent trabecular perforation with minimal collateral tissue damage and effects a significant reduction (79%) in outflow resistance.