Acute intraocular pressure response to argon laser iridotomy

Argon laser iridotomy (ALI) was performed in 50 eyes for prophylactic treatment of anatomically narrow iridocorneal angles and in 50 eyes for therapy of chronic angle-closure glaucoma. Intraocular pressure was increased 6 mmHg or more 1 to 2 hours after ALI in 19 of 50 eyes with anatomical narrow iridocorneal angles and in 23 of 50 eyes with chronic angle-closure glaucoma. Increases greater than 20 mmHg over baseline value occurred in 5 of 50 eyes with narrow iridocorneal angles and in 7 of 50 eyes with chronic angle-closure glaucoma. A clinically significant increase in intraocular pressure (defined as a pressure 30 mmHg or greater and 40% or more increased over the pre-laser value) occurred 1 to 2 hours after ALI in 11 of 50 eyes with narrow iridocorneal angles and in 17 of 50 eyes with chronic angle-closure glaucoma. There was no statistical difference (chi square P greater than 0.3) in the incidence of this complication in the two groups. Additional medical therapy was effective in lowering the acute laser-induced elevation in intraocular pressure. Patient diagnosis, patient demographics, preoperative glaucoma medication and laser treatment parameters did not predict which eyes would develop this complication. Eyes which did not have a clinically significant elevation in intraocular pressure 1 to 2 hours after ALI did not show a later increase at 24 hours.