Argon laser trabeculoplasty in narrow angle glaucoma

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Abstract
A prospective trial of argon laser trabeculoplasty (ALT) in narrow angle glaucoma (NAG) was undertaken. In eyes with NAG the mechanism of the glaucoma could be a combination of pupil block with subsequent irido-trabecular adhesion and trabecular damage with an increase in outflow resistance. To achieve relief of pupil block, eyes were randomly assigned to treatment with short pulsed laser iridotomy (LI) with the YAG or Dye lasers, or surgical peripheral iridectomy (PI). Alternatively, argon laser iridoplasty (IP) was performed to widen the anterior chamber angle sufficiently to permit ALT. Fifty-two eyes were treated and follow-up was from 12 to 22 months. A high rate of failure to control IOP with topical medication and progression of visual field loss occurred in all treatment groups. Iridoplasty followed by ALT was particularly unsuccessful as, in 50 per cent of cases, progressive synechial closure of the anterior chamber angle occurred following treatment. In eyes treated with PI/LI and ALT, the IOP control was improved in 12 per cent, unchanged in 30 per cent and remained uncontrolled in 58 per cent. By 15 months follow-up, a satisfactory outcome (IOP<21mmHg on topical medication, visual field and acuity stable) was obtained in 24 per cent of the 33 eyes treated with PI/LI and ALT. Thirty-one of these eyes showed visual field loss. Of the 10 eyes that did not receive ALT following PI or LI, 90 per cent had a satisfactory outcome. Eight of these eyes showed little or no visual field loss. The authors conclude that iridoplasty followed by ALT is an unsuitable treatment for eyes with NAG. We further conclude that ALT is unlikely to be of benefit in eyes with NAG and visual field loss, even after pupil block has been relieved. Relief of pupil block alone may help eyes with early NAG without visual field loss.