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Editors Selection IGR 16-4

Clinical forms of glaucoma: Valsalva maneuver after iridotomy

Comment by Tin Aung on:

20816 Does an iridotomy provide protection against narrowing of the anterior chamber angle during Valsalva maneuvre in eyes with primary angle closure, Sihota R; Dada T; Aggarwal A et al., Eye, 2008; 22: 389-393

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A patent laser iridotomy does not prevent irido-trabecular apposition during the Valsalva maneuver

Primary angle-closure glaucoma (PACG) is a major form of glaucoma worldwide, particularly in Asia. At the earliest stage of the disease (angle-closure suspect), eyes have narrow angles without any other abnormality. As the disease progresses, peripheral anterior synechiae and/or raised intraocular pressure (IOP) due to closure of the angle occurs, and eventually glaucomatous optic neuropathy will develop. Although anatomical risk factors for angle closure such as a shallow anterior chamber depth (ACD) have been identified, lit-tle is known about physiological mechanisms that cause angle closure or result in progression of the disease. Using ultrasound biomicroscopy (UBM), Dada et al.1 recently documented narrowing of the angle recess when the Valsalva maneuver was performed. This phenomenon was significant in eyes with narrow angles and raises the possibility that physiological actions such as the Valsalva may contribute to the angle closure process, particularly in predisposed eyes. In this study, Sihota et al. (260) evaluated angle changes during Valsalva maneuver in 23 subjects with primary angle closure and a patent laser iridotomy. IOP and pupil diameter were found to increase, and there was narrowing of the angle width but there was no change in ACD. UBM measurements of ciliary body and iris thickness also increased. The findings suggest that a patent laser iridotomy does not prevent irido-trabecular apposition during the Valsalva maneuver and raises the possibility that repeated episodes of such apposition may explain progression of angle closure disease and/or intermittent angle closure despite an iridotomy.

The study findings are interesting and will provoke more research into physiological mechanisms underlying angle closure and new risk factors for the condition. It is likely that there are multiple mechanisms involved in angle closure and possibly different subtypes of disease with varying responses to therapy.

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