Plateau Iris and Iris-Induced Angle Closure
In plateau iris and iris-induced angle closure, the peripheral iris is the cause of the iridotrabecular apposition. Iris-induced angle closure can be the direct result of developmental anomalies such as anterior cleavage abnormalities, in which the iris insertion into the scleral spur or meshwork is more anterior; a thick peripheral iris, which on dilation “rolls” into the trabecular meshwork; and/or anteriorly displaced ciliary processes (see Fig 1-9), which may secondarily rotate the peripheral iris forward (plateau iris) into the trabecular meshwork (see the section Plateau Iris later in this chapter). Though it was thought that iris-induced angle closure occurs in aniridia due to rotation of the rudimentary iris leaflets into the angle, new evidence suggests that this phenomenon occurs as a result of intraocular surgery rather than spontaneously.
Figure 9-1 Ultrasound biomicroscopy imaging. A, Eye with pupillary block showing anterior bowing of the iris. B, Eye with plateau iris anatomy showing a large, anteriorly rotated ciliary process causing appositional angle closure.
(Part A courtesy of Shan Lin, MD; part B courtesy of Sunita Radhakrishnan, MD, from the Glaucoma Center of San Francisco archives.)
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.