Iris, plateau

Medications with anticholinergic properties induce mydriasis, which can lead to angle closure in pupillary block and plateau iris. Pupillary block may also be induced by drugs that cause miosis.12... 

Figure 20-12 Plateau iris. Dilation of the pupil causes the iris to obstruct aqueous outflow, thus causing acute angle-closure glaucoma.

In I960 the concept of plateau iris was first proposed and described. Although the prevalence of plateau iris configuration is unknown, it is believed to be quite rare. 

Pavlin CJ, Ritch R, Foster FS. Ultrasound biomicroscopy in plateau iris syndrome. Am J Ophthalmol 1992 13 390-395. 

The peripheral iris profile should be observed and documented as steep, regular, concave, or plateau and the presence of iris-trabecular meshwork contact (either appositional or synechia). 

The angle of the eye is examined by gonioscopy, which requires the use of special lenses. Gonioscopy is performed to rule out angle-closure or secondary causes of lOP elevation, such as angle recession, pigmentary glaucoma, and exfoliation syndrome. The peripheral contour of the iris is examined for plateau iris, and the trabecular meshwork for peripheral anterior synechiae, as well as for neovascular or inflammatory membranes. 

CAG withont pupillary block occurs in patients with an abnormality called a plateau iris. The ciliary processes in these cases are situated anteriorly, which indent the iris forward and canse closure of the trabecular meshwork, especially during mydriasis. The mydriasis prodnced by anticholinergic dmgs or any other drng resnlts in precipitation of both types of CAG glancoma, whereas dmg-indnced miosis may prodnce pnpfllary block. 

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