Plateau Iris Definition
Plateau iris refers to two distinct clinical entities: plateau iris configuration, which is a narrow angle caused by an anteriorly positioned ciliary body with a deep central anterior chamber, and plateau iris syndrome, which is persistent iridotrabecular contact (ITC) after a patent laser peripheral iridotomy (LPI) that may cause recurrent IOP elevation. 1
Plateau Iris Configuration
Plateau iris configuration describes the anatomical appearance where the peripheral iris remains closely apposed to the angle despite a deep central anterior chamber. 1
The underlying etiology is anterior rotation or anterior positioning of the ciliary body, which mechanically pushes the peripheral iris forward against the trabecular meshwork 1, 2
This anatomical variant can be identified using dynamic gonioscopy or ultrasound biomicroscopy (UBM), but notably cannot be diagnosed with anterior segment optical coherence tomography (AS-OCT) alone 1
Approximately one-third of primary angle closure (PAC) eyes treated with iridotomy retain substantial ITC, indicating plateau iris configuration 1
Eyes with plateau iris configuration typically do not have substantial IOP increase with pupil dilation 1
The prevalence data suggests plateau iris does increase PACG risk: 8% of occludable angles have plateau iris configuration, compared to 32-37% among eyes with established PACG 1
Plateau Iris Syndrome
Plateau iris syndrome is the clinically significant form where eyes with plateau iris configuration develop recurrent high IOP spikes after iridotomy, or even after cataract extraction. 1
This represents a post-iridotomy condition where the patent iridotomy has eliminated pupillary block, yet angle closure recurs without central anterior chamber shallowing 1, 3
These patients require more extensive treatments beyond LPI, including argon laser peripheral iridoplasty, chronic miotic therapy (pilocarpine), or surgical procedures 1
Plateau iris syndrome is rare compared to plateau iris configuration 1, 4
It typically occurs in a younger age group than ordinary angle-closure glaucoma 3, 2
Key Diagnostic Distinctions
The critical difference is that plateau iris configuration is an anatomical finding that may or may not cause problems, while plateau iris syndrome is a functional diagnosis requiring documented IOP elevation or angle closure after successful iridotomy. 1
Dynamic gonioscopy in the dark room is essential for diagnosis and must be performed to verify angle configuration after treatment 1
UBM is the gold standard imaging modality as it can visualize the anteriorly positioned ciliary processes that characterize this condition 1, 5
The gonioscopic appearance shows peripheral iris closely apposed to the angle despite a deep central anterior chamber, which distinguishes it from typical pupillary block mechanisms 1