A 59-year-old Caucasian woman presents for a routine eye checkup. Her
exam is notable for slightly elevated intraocular pressures and 0.75
cupping OU. You decide to perform an anterior segment OCT which is
shown above. Which of the following statements is TRUE regarding the
most likely diagnosis?
Glaucoma
Angle Closure Glaucoma
No
U
A
The anterior segment OCT shows a narrow/closed angle but with a flat iris plane and likely deep central anterior chamber. These findings are suggestive of a plateau iris configuration which is most often caused by anteriorly positioned ciliary processes that push the peripheral iris forward.
The definitive diagnosis of plateau iris cannot be made until a
patent iridotomy is performed. A patent LPI relieves any component of
pupillary block. Thus, if the plateau iris configuration persists
despite a patent LPI, the patient can be diagnosed as having plateau
iris. However, the definitive treatment of plateau iris is not LPI, but rather it is laser iridoplasty.
This latter laser treatment involves creating slow burns to the
peripheral iris stroma so as to "pull" or contract the peripheral iris
away from the angle.
Another buzzword in plateau iris is the "sine-wave sign" whereby the iris appears to rise steeply from its insertion, but abruptly angulates away from the scleral wall.
Cycloplegics would cause peripheral iris "bunching up" and thus make the angle more narrow/closed. Conversely, chronic miotic treatment (e.g. pilocarpine) is sometimes used as an alternative or adjunct to laser iridoplasty for these eyes.
According to the BCSC, the pattern of PAS formation differ between plateau iris and pupillary block. In plateau iris, PAS formation begins at Schwalbe line and extends posteriorly while the opposite is seen in pupillary block (i.e. posterior-to-anterior direction).
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