Plateau Iris Syndrome
An angle-closure variant that persists even after a laser iridotomy, because the drainage angle is crowded by the anatomy behind the iris, not by pupil block alone.
Overview
Plateau iris syndrome is a distinctive and often under-recognized form of angle-closure glaucoma. Its defining feature is that the drainage angle remains narrow or closed even after a laser peripheral iridotomy, the procedure that resolves most narrow-angle situations.
The reason lies in the anatomy behind the iris. In most narrow angles, fluid is trapped behind the iris and pushes it forward (a mechanism called pupil block), and an iridotomy relieves this beautifully. In plateau iris, the ciliary body, the structure just behind the peripheral iris, sits unusually far forward and holds the outer edge of the iris up against the drainage meshwork. Opening a channel through the iris does not change that, so the angle stays crowded.
Symptoms
- Often no symptoms at all, discovered on careful gonioscopy or angle imaging
- A drainage angle that remains narrow after a laser iridotomy
- Intermittent blurred vision, halos, or brow ache during pressure rises
- Rarely, an acute angle-closure attack despite a prior iridotomy
How Common Is It?
Plateau iris is much less common than ordinary pupil-block angle closure, but it is an important minority of narrow-angle cases, and it is easy to miss unless it is specifically looked for. It is one of the main reasons a glaucoma specialist re-checks the angle after an iridotomy rather than assuming the problem is solved.
It tends to occur in a somewhat younger group than typical angle-closure, and more often in women.
Genetics & Risk Factors
Plateau iris reflects an inherited variation in eye anatomy, the forward position of the ciliary body, rather than a single identified gene. A family history of angle-closure or narrow angles raises the index of suspicion.
Because the trait is anatomical and often bilateral, both eyes are typically evaluated even if only one has caused trouble.
Ocular Findings on Exam
On gonioscopy, the angle appears narrow with a characteristic configuration, the iris rises steeply and then flattens (the 'plateau'), rather than bowing forward as in pupil block. After an iridotomy, the angle remains crowded, which is the key clue.
Imaging is often decisive: anterior-segment OCT or ultrasound biomicroscopy can directly show the ciliary body sitting forward and pushing the peripheral iris into the angle, confirming the diagnosis.
Testing & Diagnosis
- Gonioscopy before and after laser iridotomy to assess the angle
- Anterior-segment OCT to image the angle and iris configuration
- Ultrasound biomicroscopy to visualize the position of the ciliary body
- Intraocular pressure measurement
- Optic nerve and visual field testing to check for glaucoma damage
Treatment Options
Laser peripheral iridotomy first
Even though it is not sufficient on its own, a laser peripheral iridotomy is usually still performed, because a component of pupil block often coexists. Re-checking the angle afterward is what reveals the plateau iris component.
Laser iridoplasty
This is the signature treatment for plateau iris. Gentle laser applications to the far periphery of the iris cause it to contract and pull away from the drainage angle, physically opening the crowded space. It directly addresses the mechanism an iridotomy cannot.
Medication
Pressure-lowering eye drops help control intraocular pressure, and certain drops that constrict the pupil can pull the peripheral iris away from the angle in selected cases.
Lens surgery when appropriate
Removing the natural lens with cataract surgery deepens the front of the eye and can substantially open the angle, and is increasingly used when a cataract is also present or the angle remains dangerously narrow.
How This Differs From Other Glaucomas
The defining difference is right in the name of the problem: plateau iris is the angle closure that a laser iridotomy does not fix. Recognizing it prevents the dangerous false reassurance of thinking an eye is protected after an iridotomy when the angle is in fact still crowded.
It also calls for different tools, laser iridoplasty and angle imaging rather than iridotomy alone, which is why an accurate diagnosis matters. It is a genuine point of differentiation in glaucoma care that many general practices do not explain to patients.
The takeaway: if you have narrow angles and have already had a laser iridotomy, it is worth confirming that your angle actually opened. Plateau iris syndrome is the reason some angles stay narrow afterward, and it has its own specific, effective treatment.
Frequently Asked Questions
What is plateau iris syndrome?
Plateau iris syndrome is a form of angle-closure glaucoma in which the drainage angle stays narrow or closed even after a laser iridotomy has been performed. The iris is held forward by an unusually positioned ciliary body behind it, so opening a channel through the iris alone does not fully relieve the crowding.
How is it different from ordinary narrow-angle glaucoma?
In typical narrow-angle glaucoma, fluid backs up behind the iris (pupil block) and bows it forward; a laser iridotomy relieves this and opens the angle. In plateau iris, pupil block is not the main problem, the angle stays crowded because of the shape and position of the ciliary body, so an iridotomy alone is not enough.
Why does a laser iridotomy not fix it?
A laser peripheral iridotomy relieves pupil block by creating a tiny opening in the iris. In plateau iris, the angle is closed mainly by the ciliary body pushing the peripheral iris outward against the drainage meshwork, a mechanism the iridotomy does not address. That is why the angle can remain narrow afterward.
How is plateau iris treated?
After confirming the diagnosis, often with anterior-segment OCT or ultrasound biomicroscopy, treatment may include laser iridoplasty (using laser to contract and pull the peripheral iris away from the angle), pressure-lowering medication, and sometimes cataract or lens surgery to deepen the angle. Careful long-term monitoring is important.
Who gets plateau iris syndrome?
It tends to affect younger patients than typical angle-closure, often women, and frequently people who are found to still have narrow angles after an iridotomy. Because it can be silent, it is often discovered during careful gonioscopy or angle imaging in someone at risk.
See a glaucoma specialist. Dr. Robert Gunzenhauser is Harvard-educated and UCLA fellowship-trained in glaucoma, providing expert diagnosis and treatment for Plateau Iris Syndrome at Inland Glaucoma Center in Upland, CA.