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Editors Selection IGR 16-2

Clinical Forms of Glaucoma: Primary Angle Closure and Plateau Iris

Comment by Tin Aung & Monisha Nongpiur on:

Laser peripheral iridotomy (LPI) is the established first line treatment in the management of primary angle closure as it alleviates pupillary block, resulting in widening of the angle and flattening of iris convexity. However, LPI does not open the angles in all cases of angle closure. Persistence of angle closure in the presence of a patent iridotomy has been attributed to non-pupillary block mechanisms such as plateau iris, and lens-related factors.

In this paper, Ramakrishnan and colleagues used anterior segment optical coherence tomography (ASOCT) to assess the effect of iridoplasty in eyes that were unresponsive to LPI. Out of 252 eyes (126 patients) that underwent LPI, 24 eyes of 12 patients were found to be clinically unresponsive to LPI and were subjected to iridoplasty.

Eight of the eyes were subsequently categorized as plateau iris syndrome and the remaining 16 eyes as primary angle closure. The iridoplasty procedure resulted in a significant lowering in IOP, and widening of the angles (as documented by ASOCT). Surprisingly, the authors also found reduction in the extent of PAS, which commonly does not occur after iridoplasty. The authors should be commended for using imaging instruments such as ASOCT to evaluate response to LPI and iridoplasty. However, while ASOCT can image the anterior segment and angles, it cannot image structures posterior to the iris such as the ciliary body. Ultrasound biomicroscopy should be used for this purpose. One of the limitations of the study was the failure to specifically define ‘unresponsiveness to LPI’ in quantitative terms. It was not clear how the authors identified the 24 eyes that required further intervention.

The study emphasizes the need to evaluate the angle opening response after LPI, and in eyes with persistent closure, there is a need to consider other approaches to widen the angle such as iridoplasty in order to prevent progression of the disease.

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