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Editors Selection IGR 17-4

Clinical Forms of Glaucoma: Primary Angle Closure

Comment by Shan Lin & Marissé Masís on:

In this prospective study, the authors compared the effectiveness of argon laser peripheral iridoplasty (ALPI) versus a fixed protocol of medical treatment in patients with acute primary angle closure (APAC). Each group consisted of 15 subjects randomized to each group. Anterior segment optical coherence tomography (ASOCT) was performed before and one hour after the procedure or after medical treatment. Traditional laser peripheral iridotomy was performed when a clear media was achieved in both groups.

A greater increase in angle width was reported in the group treated with ALPI compared to the medical treatment group. Treatment modality (laser vs medical) and iris curvature were the main predictor factors influencing the anatomical change.

Acute angle closure glaucoma is a multifactorial disease given the dynamic relationship between the fluidics and the anterior segment anatomy of the eye. Several studies have been published regarding the role of ALPI as the first approach to the disease. In 2002, Lam et al.¹ published a prospective, randomized, controlled trial in which they found that ALPI is significantly more effective than conventional systemic medications in rapidly reducing IOP levels in APAC, mainly in eyes not suitable for immediate laser peripheral iridotomy within the first two hours from the initiation of treatment.

In 2012, a Cochrane-based review² summarized that there is insufficient evidence to support using iridoplasty as an adjunct to iridotomy in any form of angle closure glaucoma. Furthermore, there is not enough data related to the anterior segment effects of ALPI in APAC eyes with unclear media, a topic that is addressed by the current authors.

An important issue that needs to be taken into account is the fact that among all the anterior chamber parameters measured by ASOCT, lens vault is one of strongest predictors and causative factors for angle closure.³ In these cases a change on the anterior surface of the iris from ALPI may not be beneficial to the patient in the long term.

The presence of peripheral anterior synechiae and the amount of persistent appositional angle closure can also contribute to the long-term failure of ALPI or may determine the need for secondary treatment in a longer follow-up period. Naravanaswamy et al. published in 2016 a study that supported that after a one-year follow-up, ALPI was associated with higher failure rates and lower IOP reduction compared with medical therapy in chronic angle closure.⁴ The clinical benefit of ALPI for APAC is still being determined.

Causal influence should be taken into account when deciding a therapeutic approach. In acute angle closure with no clear media, the treatment options are initially limited. This novel study may lead to further clinical investigations of ALPI as an adjunctive therapy, mainly in patients with systemic contraindications to the use of medical treatment.

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