Biphasic Intraocular Pressure Response to Laser Irradiation of the Iris in Rabbits

Abstract

The possibility of an acute increase in intraocular pressure (IOP) following laser iridotomy is well known. However, little attention has been paid to the hypotony after laser irradiation of the iris. We performed this study to evaluate the effect of laser irradiation of the iris on the IOP in pigmented rabbits. IOP, aqueous flare values, and aqueous prostaglandin E₂ levels were measured before and 1,4, 12, and 24 h after argon laser treatment. The IOP showed a prolonged reduction for 24 h following an initial transient increase. Flare values and aqueous prostaglandin E₂ levels reached a peak 1 h after laser treatment, followed by a progressive reduction. Argon laser peripheral iridoplasty that can separate the iris from the trabecular meshwork by the mechanical force resulting from a contraction burn is used sometimes in treating angle-closure glaucoma. Our results showed that the laser irradiation of the iris itself can cause ocular hypotony, so that this phenomenon may be another explanation of the IOP response after peripheral iridoplasty.

Influence of laser irradiation on endogenous hyaluronan in rabbit iris and aqueous humor

“…The changes of aqueous protein and aqueous flare response in laser treated eyes in the present study are similar to previous observations (Kim & Lee 1995; Schrems et al 1983a) and are as expected after blood‐aqueous barrier breakdown after laser irradiation.…”

“…It is well documented that laser irradiation of the iris results in blood‐aqueous barrier breakdown with symptoms like protein leakage to the anterior chamber and an aqueous flare response (Kim & Lee 1995; Unger 1990; Schrems et al 1983a, 1983b) but, to our knowledge, there are no previous reports on hyaluronan changes after laser irradiation.…”

“…The argon laser technique used in this experiment is a well‐known procedure in the treatment of certain cases of glaucoma. The irradiation of the anterior surface of the iris induces a release of prostaglandins from iris and ciliary body, resulting in a breakdown of the blood‐aqueous barrier and consequently also a leakage of proteins to the aqueous humor (Kim & Lee 1995; Unger 1990). The technique has been shown to be a convenient way to generate a reproducible ocular injury response (Gherezghiher & Koss 1989).…”