Plateau Iris Glaucoma

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Background

Plateau iris is one of the most common angle-closure glaucomas presenting in younger patients. This condition is characterized by closing of the anterior chamber angle secondary to a large or anteriorly positioned ciliary body that mechanically alters the position of the peripheral iris in relation to the trabecular meshwork.

Pathophysiology

In plateau iris configuration, the pars plicata may be large and anteriorly positioned, mechanically positioning the peripheral iris against the trabecular meshwork. In addition, the iris root is inserted anteriorly on the ciliary face further crowding the anterior chamber angle. The iris crowding of the angle obstructs aqueous flow via the trabecular meshwork and may lead to angle-closure glaucoma.

Except in the rare younger patients (age 20-30s), some degree of pupillary block also is present. Because a component of pupillary block may exist in patients with plateau iris configuration, laser iridotomy should always be performed as the first intervention. If the angle remains capable of closure despite a patent iridotomy, the condition is termed plateau iris syndrome.

A high prevalence of plateau iris configuration and plateau iris syndrome has been reported in relatives of patients with plateau iris syndrome. An autosomal dominant inheritance pattern with incomplete penetrance has also been suggested.[1]

Epidemiology

Frequency

United States

The exact prevalence of plateau iris is unknown. A 2016 study found that one third of eyes with primary angle-closure glaucoma had plateau iris.[2] In another report, it accounted for more than half of recurrent angle closure cases in young patients.[3] The diagnosis of plateau iris should be suspected when angle closure occurs in patients who are young or myopic and when angle narrowing persists despite iridotomy.

International

In a study from Singapore, plateau iris was found in about a third of primary angle closure suspects older than 50 years of age after laser iridotomy.[4] Another study found that 20% of Japanese patients with primary angle closure after laser iridotomy had plateau iris based on ultrasound biomicroscopy.[5]

Mortality/Morbidity

Plateau iris is an important cause of angle-closure glaucoma in patients younger than 50 years.

Race

Studies reported no difference in prevalence of plateau iris between whites and Asians.[6, 7]

Sex

Plateau iris is seen most commonly in women.

Age

Patients with plateau iris usually are younger than those with primary angle-closure (relative pupillary block) glaucoma.

History

Patients with plateau iris tend to be female, in their 30-50s, hyperopic, and often have a family history of angle-closure glaucoma.

Patients may present with angle closure, either spontaneously or after pupillary dilation.

More commonly, the diagnosis of plateau iris configuration is made on routine examination.

Plateau iris syndrome usually is recognized in the postoperative period when the angle remains persistently narrow in an eye after iridotomy.

Physical

Slit lamp examination of patients with plateau iris usually shows normal anterior chamber depth with a flat or slightly convex iris surface.

On gonioscopy, the angle is extremely narrowed or closed, with a sharp drop-off of the peripheral iris. When indentation gonioscopy is performed, the double-hump sign is seen. The more peripheral hump is determined by the ciliary body propping up the iris root, and the more central hump represents the central third of the iris resting over the anterior lens surface. The space between the humps represents the space between the ciliary processes and the endpoint of contact of the iris to the anterior lens capsule. More force often is needed to open the angle on indentation gonioscopy than on pupillary block angle closure.

Plateau iris syndrome is characterized by persistent angle occludability (spontaneous, in the dark, or after dilation) in an eye with a patent iridotomy. The level of the iris stroma in relation to the angle structures, referred to as the height of the plateau, differentiates the 2 subtypes of plateau iris syndrome.

In the complete syndrome, the angle is occluded to the upper trabecular meshwork or the Schwalbe line and intraocular pressure (IOP) rises.

Incomplete plateau occludes the angle to mid level, leaving the upper portion of the filtering meshwork open and IOP unchanged. This latter situation is far more common and is clinically important because these patients can develop peripheral anterior synechiae (PAS) and synechial angle closure years after a successful iridotomy. Therefore, patients with open angle after iridotomy should not be assumed to be cured. The angle can narrow further with age, and angle closure can occur years later.

Causes

Plateau iris results from large or anteriorly positioned ciliary processes holding forward the peripheral iris and maintaining its apposition to the trabecular meshwork. The etiology underlying this anterior displacement of the pars plicata is unclear but probably represents an anatomic variant.

No indication exists of any abnormality of the ciliary body that would cause such forward rotation of the ciliary processes. The possibility that the lens-zonule apparatus is pulling the process forward is unlikely because of the observation that in pseudophakic patients the iris processes remain in a forward position, despite the posterior position of the posterior chamber lens.

Imaging Studies

Ultrasound biomicroscopy

The configuration of the iris surface, iris root insertion, iridocorneal angle, and ciliary processes can be seen in detail to confirm the clinical findings of plateau iris (this is shown in the image below).[9, 10, 11]



View Image

Ultrasound biomicroscopy. (A) In plateau iris, the anterior position of the ciliary body holds the peripheral iris against the trabecular meshwork. (B....

Any element of pupillary block also may be confirmed with ultrasound biomicroscopy (UBM) imaging.

Cysts or uncommon mass of the iris or ciliary body may be identified as the underlying cause of narrow angle (pseudoplateau iris).

Optical coherence tomography

Optical coherence tomography (OCT) has evolving utility in imaging anterior segment structures and may assist in diagnosing plateau iris.[12, 13]

Medical Care

Surgical management is the primary treatment modality in patients with plateau iris configuration or syndrome. However, pilocarpine may produce iris thinning and facilitate angle opening in some cases.

Surgical Care

Because some degree of pupillary block frequently exists in patients with plateau iris configuration, peripheral laser iridotomy always should be performed as the first intervention in all patients suspected of having plateau iris.

A patent iridotomy may be therapeutic in reducing risks of angle closure. However, in some patients, laser iridotomy may not significantly alter the anterior chamber depth or anatomy. Even after a successful iridotomy produces what appears to be a well-opened angle, periodic gonioscopy remains crucial because these patients may have incomplete plateau iris syndrome or the angle may narrow further with age because of the enlargement of the lens. Although usually recognized in the postiridotomy period, plateau iris syndrome may develop years later. Patients with plateau iris configuration should not be assumed to be cured, even though plateau iris syndrome does not develop immediately.

Images before and after laser iridotomy are shown below.



View Image

Ultrasound biomicroscopy, plateau iris syndrome. (A) Appositional anterior chamber angle in dark condition prior to laser iridotomy. (B) After laser i....

Peripheral laser iridoplasty

If persistent iridotrabecular apposition is present despite a patent iridotomy, the diagnosis is consistent with plateau iris syndrome, and peripheral laser iridoplasty is indicated.

Argon laser peripheral iridoplasty (ALPI) is the procedure of choice to effectively open an angle that remains occluded after successful laser iridotomy. The procedure consists of placing laser burns on the surface of the peripheral iris to contract the iris stroma between the site of the burn and the angle. Peripheral location of long-duration, low-power, large spot size laser burns is essential for success. The result is iris stromal tissue contraction and compaction that physically widens the angle and prevents the apposition of the peripheral iris against the trabecular meshwork.[14] More recent optic coherence tomography studies suggest that thinning of the iris after ALPI also contributes to opening of the angle.[15]

ALPI is highly effective, and the effect is maintained for years. However, even after successful opening of the angle, regular gonioscopic examination remains crucial. A small proportion of patients may develop reclosure of the angle, which is readily reopened with repeat ALPI. Urrets-Zavalia syndrome (prolonged mydriasis unresponsive to pilocarpine) is an uncommon complication of ALPI that typically resolves spontaneously within 1 year.[16]

Other surgical intervention

If angle closure persists despite iridotomy and sufficient peripheral laser iridoplasty, surgical intervention in the form of lens extraction, endoscopic laser cycloplasty, goniosynechialysis, trabeculectomy, or tube-shunt implantation surgery may be needed to open the anterior chamber angle, allow bypass of aqueous flow, and control IOP.[17, 18]

Consultations

Consultation and/or comanagement with a glaucoma specialist may be helpful in patients who fail to respond to laser iridotomy and iridoplasty.

Medication Summary

Treatment of plateau iris is primarily surgical. However, in patients whose anterior chamber angles remain occludable after properly performed iridotomy and laser peripheral iridoplasty, miotic therapy may be used to prevent angle closure.

Pilocarpine ophthalmic (Pilocar, Piloptic, Pilostat, Akarpine, Ocusert Pilo-40)

Clinical Context:  Commercially available as an ophthalmic solution, daily dosing gel, and sustained-release membranes (Ocusert). The symptoms of induced myopia and miosis are best tolerated with the sustained-release Ocusert.

Class Summary

Miotic agents cause the pupillary sphincter to contract, mechanically pulling the iris away from the trabecular meshwork and opening the anterior chamber angle. In addition, these agents also have an IOP-lowering effect by stimulating contraction of the ciliary muscle and thereby increasing trabecular outflow of aqueous humor. Induced myopia, pupillary constriction, brow ache, and retinal detachment are potential adverse effects of this therapy.

Further Outpatient Care

Periodic gonioscopy remains crucial because patients may develop further angle narrowing or closure years after achieving open-angle with patent iridotomy.

Routine follow-up screening for development of glaucoma also is recommended.

Complications

Plateau iris causes crowding of the anterior chamber angle and may lead to acute or chronic angle-closure glaucoma even in the presence of a patent iridotomy.

Prognosis

Patients with plateau iris have a good prognosis in general; however, regular follow-up examinations are needed because angle-closure may develop years after successful iridotomy or iridoplasty.

Patient Education

For excellent patient education resources, visit eMedicineHealth's Eye and Vision Center. Also, see eMedicineHealth's patient education articles Glaucoma Overview, Glaucoma FAQs, and Glaucoma Medications.

Author

Jim C Wang (王崇安), MD, Vitreo-Retinal and Cornea/Anterior Segment Subspecialist, Department of Ophthalmology, Kaiser Permanente Fontana Medical Center

Disclosure: Nothing to disclose.

Coauthor(s)

Paul S Lee, MD, Clinical Assistant Professor, Department of Ophthalmology, Mount Sinai School of Medicine; Chief of Ophthalmology, James J. Peters Veterans Affairs Medical Center; Associate Adjunct Surgeon, New York Eye and Ear Infirmary

Disclosure: Nothing to disclose.

Robert Ritch, MD, FACS, FARVO, Shelley and Steven Einhorn Distinguished Chair in Ophthalmology, Professor of Ophthalmology, Surgeon Director Emeritus, New York Eye and Ear Infirmary of Mount Sinai

Disclosure: Received none from Sensimed for board membership; Received none from iSonic Medical for board membership; Received consulting fee from Aeon Astron for consulting; Received honoraria from Pfizer for speaking and teaching; Received honoraria from Allergan for speaking and teaching; Received honoraria from Ministry of Health of Kuwait for speaking and teaching; Received honoraria from Aeon Astron for speaking and teaching; Received royalty from Ocular Instruments for other.

Specialty Editors

Francisco Talavera, PharmD, PhD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Martin B Wax, MD, Professor, Department of Ophthalmology, University of Texas Southwestern Medical School; Vice President, Research and Development, Head, Ophthalmology Discovery Research and Preclinical Sciences, Alcon Laboratories, Inc

Disclosure: Nothing to disclose.

Chief Editor

Hampton Roy, Sr, MD, Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences

Disclosure: Nothing to disclose.

Additional Contributors

Bradford Shingleton, MD, Assistant Clinical Professor of Ophthalmology, Harvard Medical School; Consulting Staff, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary

Disclosure: Nothing to disclose.

Acknowledgements

Celso Tello, MD Clinical Assistant Professor, Department of Ophthalmology, New York Eye and Ear Infirmary

Celso Tello, MD is a member of the following medical societies: American Academy of Ophthalmology, American Medical Association, and New York Academy of Sciences

Disclosure: Nothing to disclose.

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Ultrasound biomicroscopy. (A) In plateau iris, the anterior position of the ciliary body holds the peripheral iris against the trabecular meshwork. (B) The angle is obstructed further in the dark as the peripheral iris thickens with physiologic pupillary dilation.

Ultrasound biomicroscopy, plateau iris syndrome. (A) Appositional anterior chamber angle in dark condition prior to laser iridotomy. (B) After laser iridotomy, the angle remains occludable. (C) After peripheral laser iridoplasty, the peripheral iris is thinned, opening the angle and significantly reducing the risk of closure.

Ultrasound biomicroscopy. (A) In plateau iris, the anterior position of the ciliary body holds the peripheral iris against the trabecular meshwork. (B) The angle is obstructed further in the dark as the peripheral iris thickens with physiologic pupillary dilation.

Ultrasound biomicroscopy, plateau iris syndrome. (A) Appositional anterior chamber angle in dark condition prior to laser iridotomy. (B) After laser iridotomy, the angle remains occludable. (C) After peripheral laser iridoplasty, the peripheral iris is thinned, opening the angle and significantly reducing the risk of closure.