Ophthalmology – Plateau Iris Glaucoma

Basics

Description

Plateau iris is an anatomic configuration that predisposes to angle closure despite a relatively normal central anterior chamber depth.

The mechanism is primarily:

Anteriorly positioned and/or enlarged ciliary processes → peripheral iris pushed forward → crowding of the iridocorneal angle

Unlike conventional pupillary-block angle closure, the central iris may appear relatively flat.

A key feature is that the angle may remain:

Narrow or occludable despite a patent laser peripheral iridotomy (LPI).

Important Terminology

Two related terms should be distinguished:

Plateau Iris Configuration

An anatomic appearance characterized by:

• Relatively deep or normal central anterior chamber
• Flat central iris plane
• Abrupt peripheral iris angulation
• Narrow/occludable angle

It may exist before or after LPI.

Plateau Iris Syndrome

Refers to clinically significant angle closure that:

• Persists or recurs after a patent LPI
• Cannot be explained by residual pupillary block alone

It may cause:

• IOP elevation
• Peripheral anterior synechiae
• Acute angle closure
• Chronic angle-closure glaucoma

Key Clinical Concept

Think of plateau iris when:

The central anterior chamber looks reasonably deep, but gonioscopy shows a very narrow or closed peripheral angle.

This is why slit-lamp estimation alone can miss the diagnosis.

Epidemiology

Plateau iris anatomy is not rare among patients with:

• Primary angle-closure suspect
• Primary angle closure
• Angle-closure glaucoma

It is often detected in:

• Younger patients than typical pupillary-block angle closure
• Women
• Patients in their 30s–50s

It can occur across different refractive groups.

Risk Factors

Associations include:

• Female sex
• Younger age relative to conventional angle-closure patients
• Family history of angle closure
• Anteriorly positioned ciliary processes

Unlike classic pupillary-block angle closure:

Marked hyperopia is not required.

Plateau iris can occur in:

• Emmetropic
• Mildly hyperopic
• Occasionally myopic eyes

Pathophysiology

The ciliary processes are positioned:

• Anteriorly
• Close to the posterior iris

This supports the peripheral iris from behind and pushes it toward the trabecular meshwork.

The resulting configuration produces:

• Peripheral angle crowding
• Iridotrabecular contact
• Potential synechial closure

Role of Pupillary Block

A patient with plateau iris may also have:

A component of pupillary block

Therefore, LPI is generally performed first in an occludable angle.

After LPI:

• Pupillary block is relieved
• Any residual angle closure reflects non-pupillary-block anatomy, such as plateau iris

Persistent Angle Narrowing After LPI

This is the classic clue:

Patent LPI + persistent narrow/closed angle = consider plateau iris

Other causes of persistent angle closure must also be excluded.

Pseudoplateau Iris

A plateau-like configuration may be caused by:

• Multiple ciliary body cysts
• Iris cysts
• Ciliary body tumor or mass

This is termed:

Pseudoplateau iris

UBM is especially useful for distinguishing true plateau iris from these conditions.

Clinical Presentation

Many patients are:

Asymptomatic

and are discovered during routine gonioscopy.

Others may experience:

• Intermittent blurred vision
• Halos
• Ocular pain
• Headache

particularly after:

• Pharmacologic dilation
• Dark adaptation
• Other circumstances causing pupillary enlargement

Acute Angle Closure

Plateau iris can produce an acute attack with:

• Severe ocular pain
• Red eye
• Blurred vision
• Halos
• Headache
• Nausea
• Vomiting

Examination may show:

• Corneal edema
• Elevated IOP
• Mid-dilated pupil
• Closed angle

Chronic Disease

Repeated or prolonged iridotrabecular contact can produce:

• Peripheral anterior synechiae (PAS)
• Chronic angle closure
• Persistent elevation of IOP
• Glaucomatous optic neuropathy

Slit-Lamp Examination

The central anterior chamber often appears:

• Normal or only mildly shallow

The iris may look:

• Relatively flat centrally

This contrasts with the more uniformly convex iris seen in classic pupillary-block angle closure.

Van Herick Testing

Van Herick estimation can be misleading.

A patient may have:

• Reasonably preserved peripheral chamber depth by slit lamp

yet still have significant angle crowding on gonioscopy.

Therefore:

Van Herick examination cannot exclude plateau iris.

Gonioscopy

Gonioscopy is essential for diagnosis.

Typical findings include:

• Narrow or closed angle
• Steep peripheral iris insertion
• Relatively flat central iris
• Persistent appositional closure after LPI

Indentation gonioscopy is particularly useful.

Double-Hump Sign

The classic gonioscopic sign is the:

Double-hump sign

During indentation:

• First hump = peripheral iris overlying the ciliary body
• Second hump = iris overlying the lens
• A depression lies between them

This strongly supports plateau iris configuration.

Indentation Gonioscopy

Indentation helps distinguish:

Appositional Closure

The angle opens with indentation.

Synechial Closure

The angle remains closed because of:

Peripheral anterior synechiae

This distinction affects prognosis and management.

Peripheral Anterior Synechiae

PAS may develop from repeated or chronic contact between:

• Peripheral iris
• Trabecular meshwork

Extensive PAS can produce:

Chronic angle-closure glaucoma

even after the initial plateau mechanism is treated.

Ultrasound Biomicroscopy

UBM is the best imaging modality for demonstrating the ciliary body anatomy underlying plateau iris.

Typical findings include:

• Anteriorly positioned ciliary processes
• Absent or reduced ciliary sulcus
• Peripheral iris pushed anteriorly
• Iridotrabecular contact
• Relatively flat central iris

Why UBM Is Important

UBM directly images structures posterior to the iris, including:

• Ciliary body
• Ciliary processes

It is particularly useful when:

• Diagnosis is uncertain
• Pseudoplateau iris is suspected
• Angle remains narrow after LPI

Anterior Segment OCT

AS-OCT is useful for demonstrating:

• Narrow angle
• Iridotrabecular contact
• Central anterior chamber depth
• Iris configuration

However:

AS-OCT generally cannot image the ciliary body as well as UBM

and therefore may suggest but not fully establish the mechanism.

Optic Nerve Evaluation

Assess for glaucomatous damage with:

• Optic disc examination
• RNFL OCT
• Macular GCIPL/GCC
• Visual fields

Plateau iris anatomy alone does not equal glaucoma.

Plateau Iris Configuration vs Plateau Iris Glaucoma

Plateau Iris Configuration

• Narrow/occludable angle
• No definite glaucomatous damage required

Plateau Iris Syndrome

• Persistent/recurrent angle closure after patent LPI

Plateau Iris Glaucoma

• Plateau iris mechanism
• Elevated IOP and/or PAS
• Glaucomatous optic neuropathy with corresponding functional damage

Differential Diagnosis

Important differentials include:

• Pupillary-block angle closure
• Phacomorphic glaucoma
• Aqueous misdirection
• Pseudoplateau iris from ciliary body cysts
• Ciliary body tumor
• Lens subluxation
• Choroidal effusion

Plateau Iris vs Pupillary-Block Angle Closure

Plateau Iris

• Relatively deep central chamber
• Flat central iris
• Abrupt peripheral iris rise
• Angle may remain narrow after LPI
• Double-hump sign

Pupillary Block

• More uniformly convex iris
• Shallower central chamber
• Angle usually widens substantially after LPI

Plateau Iris vs Phacomorphic Glaucoma

Phacomorphic glaucoma typically shows:

• Intumescent cataract
• Markedly shallow anterior chamber
• Large lens component
• Acute secondary angle closure

Plateau iris typically has:

• More normal central chamber depth
• Characteristic ciliary body configuration

Plateau Iris vs Aqueous Misdirection

Aqueous misdirection usually shows:

• Diffuse shallowing of both central and peripheral anterior chamber
• Often follows ocular surgery
• Patent iridotomy
• Anterior displacement of lens–iris diaphragm

This differs from the relatively preserved central chamber in plateau iris.

Treatment Principles

Management has several goals:

1. Eliminate any pupillary-block component.
2. Open the peripheral angle.
3. Prevent PAS formation.
4. Control IOP.
5. Prevent glaucomatous optic neuropathy.

Laser Peripheral Iridotomy

For an occludable angle with suspected plateau iris:

LPI is generally performed first

because pupillary block commonly coexists.

LPI:

• Equalizes pressure between posterior and anterior chambers
• Removes the pupillary-block component

Important Principle After LPI

A patent LPI does not cure the underlying ciliary-body anatomy of plateau iris.

If the angle remains occludable after LPI:

Residual plateau iris should be considered.

Argon Laser Peripheral Iridoplasty

Laser peripheral iridoplasty is the classic treatment for residual appositional angle closure from plateau iris after LPI.

It is also called:

Laser iridoplasty

Modern lasers other than argon may be used depending on equipment.

Mechanism of Iridoplasty

Laser burns are placed in the far peripheral iris.

Thermal contraction causes:

• Peripheral iris thinning
• Stromal contraction
• Pulling of the iris away from the trabecular meshwork

This widens the angle.

Indications for Iridoplasty

Consider ALPI when there is:

• Persistent occludable angle after LPI
• Plateau iris syndrome
• Recurrent angle closure after LPI
• Persistent appositional iridotrabecular contact

Limitations of Iridoplasty

Iridoplasty:

• Does not remove the underlying anterior ciliary processes
• May lose effectiveness over time
• Does not reverse established PAS

Some patients require:

• Repeat treatment
• Additional glaucoma therapy

Pilocarpine

Low-dose pilocarpine may:

• Constrict the pupil
• Pull the peripheral iris away from the angle

and can reduce angle closure.

However, chronic pilocarpine is now used less often because of:

• Brow ache
• Accommodative spasm
• Induced myopia
• Reduced night vision
• Retinal traction concerns

It is generally a:

Selective or temporary therapy rather than preferred long-term management.

Acute Angle-Closure Attack

If plateau iris presents with acute angle closure, initially treat as an acute angle-closure emergency.

Therapy may include:

• Topical beta-blocker
• Alpha-2 agonist
• Topical carbonic anhydrase inhibitor
• Systemic acetazolamide
• Hyperosmotic agent if required
• Topical corticosteroid

Pilocarpine During Acute Attack

Pilocarpine may be used after IOP has begun to fall and iris perfusion improves.

At extremely high IOP:

• Iris sphincter ischemia may make pilocarpine ineffective

LPI After Acute Attack

Once corneal edema and IOP permit:

LPI should be performed to remove any pupillary-block component.

The angle must then be reassessed.

If it remains narrow:

• Plateau iris syndrome is likely
• Iridoplasty may be required

Dilation After LPI

Pharmacologic dilation may precipitate angle closure in plateau iris.

Historically, a formal dilation challenge was sometimes used.

Modern practice generally favors:

• Repeat gonioscopy
• IOP assessment
• Anterior segment imaging

rather than deliberately provoking angle closure solely for diagnosis.

Lens Extraction

Lens extraction deepens the anterior chamber and can reduce angle crowding.

It is particularly useful when there is:

• Cataract
• Significant lens component
• Coexisting pupillary-block anatomy

Important Lens Extraction Principle

Unlike pure lens-induced angle closure:

Cataract extraction may not completely eliminate plateau iris anatomy

because the primary abnormality is the:

• Ciliary body
• Ciliary process position

Residual angle narrowing can remain after lens extraction.

Clear-Lens Extraction

Clear-lens extraction is not routinely required solely because plateau iris configuration is present.

It may be considered in selected patients with:

• Recurrent angle closure
• Significant lens-related crowding
• Poor control with laser/medical treatment

Treatment should be individualized.

Chronic Angle-Closure Glaucoma

If extensive PAS or permanent trabecular damage develops, management follows principles of chronic angle-closure glaucoma.

Options may include:

• IOP-lowering medications
• Lens extraction when appropriate
• Goniosynechialysis in selected cases
• Glaucoma surgery

Glaucoma Medications

If IOP remains elevated, options include:

• Prostaglandin analogs
• Beta-blockers
• Carbonic anhydrase inhibitors
• Alpha-2 agonists

The treatment target depends on:

• Optic nerve damage
• Visual field loss
• Disease progression

Goniosynechialysis

In selected eyes with relatively recent PAS, goniosynechialysis may be performed, often at the time of:

Lens extraction

to restore trabecular access.

Long-standing PAS is less likely to respond.

Filtering / Glaucoma Surgery

If IOP remains uncontrolled despite:

• LPI
• Iridoplasty
• Lens management
• Medications

surgical options may include:

• Trabeculectomy
• Glaucoma drainage device
• Other glaucoma procedures depending on anatomy

Follow-Up

Patients require ongoing surveillance even after successful:

• LPI
• Iridoplasty
• Cataract surgery

because the angle can narrow again.

Monitoring

Follow-up should include:

• IOP
• Gonioscopy
• LPI patency
• PAS assessment
• Optic nerve examination
• OCT
• Visual fields when glaucoma is present

Gonioscopy

Serial gonioscopy is essential.

Look for:

• Increasing iridotrabecular contact
• New PAS
• Progressive angle narrowing

A patent LPI does not remove the need for gonioscopic surveillance.

Dilation

Before routine dilation in a patient with plateau iris:

• Confirm angle status
• Confirm LPI patency when applicable

After dilation, selected high-risk patients may benefit from:

• IOP reassessment

Prognosis

Most patients do well when:

• Anatomy is recognized early
• Pupillary block is treated
• Persistent peripheral closure is identified
• IOP is controlled

Visual prognosis depends primarily on whether:

Glaucomatous optic nerve damage has already occurred.

Complications

Potential complications include:

• Acute angle-closure attack
• Recurrent angle closure
• Peripheral anterior synechiae
• Chronic angle-closure glaucoma
• Progressive glaucomatous optic neuropathy
• Visual field loss

Ophthalmology Pearls

• Plateau iris is caused by anteriorly positioned ciliary processes that push the peripheral iris forward and crowd the angle.
• The central anterior chamber can look relatively normal, so Van Herick examination alone can miss the diagnosis.
• The key diagnostic test is gonioscopy with indentation.
• The classic gonioscopic finding is the double-hump sign.
• Plateau iris configuration describes the anatomy; plateau iris syndrome describes persistent or recurrent angle closure after a patent LPI.
• Perform LPI first when an occludable angle is present because pupillary block commonly coexists.
• A patent LPI with persistent angle narrowing strongly suggests a non-pupillary-block mechanism such as plateau iris.
• UBM is particularly useful because it directly demonstrates the anteriorly positioned ciliary processes and can identify ciliary body cysts causing pseudoplateau iris.
• AS-OCT can document angle closure but is less effective than UBM for imaging the ciliary body.
• Laser peripheral iridoplasty is the classic treatment for persistent appositional closure after LPI.
• Chronic pilocarpine is now used selectively because of significant adverse effects.
• Lens extraction can deepen the angle, especially when cataract or lens crowding coexists, but it may not completely eliminate true plateau iris anatomy.
• Even after LPI or iridoplasty, long-term gonioscopic surveillance is essential because PAS and chronic angle-closure glaucoma can still develop.