Plateau iris refers to an atypical configuration of the anterior chamber angle that may result in angle-closure disease. It is a common finding in younger subjects with angle closure. Evidence suggests that plateau iris configuration may result from more anteriorly positioned ciliary processes, which can be seen as an absence of the ciliary sulcus on ultrasound biomicroscopy (UBM) imaging. Angle closure in plateau iris is most often caused by these anteriorly positioned ciliary processes severely narrowing the anterior chamber recess by pushing the peripheral iris forward. A component of pupillary block is often present. The angle may be further compromised following dilation of the pupil, as the peripheral iris crowds and obstructs the trabecular meshwork.
Plateau iris may be suspected if the central anterior chamber appears to be of normal depth, and the iris plane appears flat for an eye with angle closure. This suspicion can be confirmed by the presence of the “double-hump” sign on gonioscopy (the iris is indented by the anteriorly situated ciliary processes, creating the appearance of a hump in the iris contour during indentation gonioscopy) or by ultrasound biomicroscopy (see Fig 3-9). The condition will be missed if the examiner relies solely on slit-lamp examination or the Van Herick method of angle examination.
Plateau iris configuration is the term used to describe an eye with gonioscopic and/or imaging evidence of plateau iris in which a mydriatic provocative test does not induce IOP elevation. Conversely, in plateau iris syndrome, pharmacologic mydriasis induces IOP elevation of 6 mm Hg or more. In plateau iris syndrome, PAS formation has been reported to begin at the Schwalbe line (see Fig 3-9) and then to extend in a posterior direction over the trabecular meshwork, scleral spur, and angle recess. The reverse is seen in pupillary block–induced angle closure, in which synechiae form in the posterior-to-anterior direction.
The initial management of plateau iris includes either laser iridotomy to remove any component of pupillary block or lensectomy if cataract is present. Eyes with plateau iris configuration may be monitored without further intervention. Eyes with plateau iris syndrome remain predisposed to angle closure—and possible acute attack—despite a patent iridotomy because of the peripheral iris anatomy. Plateau iris syndrome is the most common reason for a persistently narrow or occludable angle after LPI or cataract surgery. Thus, careful assessment of the angle following iridotomy or lensectomy is necessary to determine whether additional treatment is required to further deepen the angle. Combined lensectomy and endoscopic cyclophotocoagulation (ECP) can also be utilized to deepen the angle in plateau iris, as ECP causes the collagen fibers to contract and shrinks the ciliary processes, and may also rotate the ciliary processes posteriorly away from the peripheral iris.
Patients with plateau iris syndrome may be treated with long-term miotic therapy. However, laser peripheral iridoplasty may be more useful in individuals with this condition to flatten and thin the peripheral iris (see Fig 3-9 and Chapter 13). Repeated gonioscopy at regular intervals is necessary because the risk of chronic angle closure remains despite measures to deepen the angle recess. The management of plateau iris syndrome is evolving, and further research is needed to determine the optimal management of this condition.
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Kumar RS, Tantisevi V, Wong MH, et al. Plateau iris in Asian subjects with primary angle closure glaucoma. Arch Ophthalmol. 2009;127(10):1269–1272.
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Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.