The effect of alpha2-agonist on IOP rise following Nd-YAG laser iridotomy

We have tested the effect of topical administration of 0.5% para-amino-clonidine (PAC), an adrenergic alpha 2 agonist, on intraocular pressure (IOP), protein and prostaglandin E2 (PGE2) concentration in aqueous humor following the laser application to the iris of albino rabbits. The irides received Q-switched Nd: YAG laser irradiation with the energy level ranging from 2 to 80 mJ with and without topical administration of PAC one-hour prior to and immediately following laser irradiation. The IOP was measured with an Alcon pneumotonometer prior to and hourly for 6-hours following laser application. Aqueous humor was withdrawn prior to and at 0.5, 1, 2, 4 hours following laser irradiation for determining protein (Lowry method) and PGE2 (radioimmunoassay). Four to 6 rabbits were used for each experiment. The increase in IOP, protein and PGE2 concentration following laser irradiation was demonstrated to be dependent on the amount of laser energy. PAC significantly suppressed the IOP rise and the elevation of protein content, while it failed to affect the increase in PGE2.