Histological study on transient ocular hypertension after laser iridotomy in rabbits.

We performed argon-laser iridotomy on pigmented rabbits and examined histologically the tissue of the anterior chamber angle, the iris, and the ciliary body. After laser iridotomy, 9/10 eyes showed an elevation in transient intraocular pressure. Deposits of blood plasma with fibrin were observed in the tissue of the circumferential anterior chamber angle from eyes enucleated at a period of high intraocular pressure. In the eyes in which ocular pressures returned to the baseline, the quantity of blood plasma was small. In the laser-irradiated iris and iris processes, cells constructing the vessel wall were degenerated, and blood plasma and fibrin exuded. In and around the ciliary body, fibrin was not demonstrated. These observations suggest that argon-laser irradiation to the iris leads to a breakdown of the blood-aqueous barrier mainly in the laser-treated iris, and that deposition of blood plasma with fibrin in the anterior chamber angle tissue may cause transient intraocular pressure elevations after laser iridotomy in rabbits.