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Ophthalmology > INTRAOCULAR PRESSURE
Glaucoma, Plateau Iris
Article Last Updated: Feb 11, 2008
AUTHOR AND EDITOR INFORMATION
Section 1 of 11  
Author: Jim C Wang, MD, Retina/Vitreous Fellow, Department of Ophthalmology, West Virginia University; Cornea/Anterior Segment Subspecialist, Department of Ophthalmology, Kaiser Permanente Fontana Medical Center
Jim C Wang is a member of the following medical societies: American Academy of Ophthalmology, American Society of Cataract and Refractive Surgery, and American Society of Retina Specialists
Coauthor(s):
Robert Ritch, MD, Chief of Glaucoma Service, Surgeon Director, Professor, Department of Ophthalmology, New York Eye and Ear Infirmary;
Celso Tello, MD, Clinical Assistant Professor, Department of Ophthalmology, New York Eye and Ear Infirmary
Editors: Bradford Shingleton, MD, Assistant Clinical Professor of Ophthalmology, Harvard Medical School; Consulting Staff, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Martin B Wax, MD, Clinical Professor, Department of Ophthalmology, University of Texas Southwestern Medical School; Vice President, Ophthalmology Research and Development, Head, Ophthalmology Discovery Research, Alcon Labs, Inc; Lance L Brown, OD, MD, Ophthalmologist, Affiliated With Freeman Hospital and St John's Hospital, Regional Eye Center, Joplin, Missouri; Hampton Roy Sr, MD, Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences
Author and Editor Disclosure
Synonyms and related keywords:
plateau iris, plateau iris syndrome, plateau iris configuration
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 has been reported in relatives of patients with plateau iris syndrome. An autosomal dominant inheritance pattern with incomplete penetrance has also been suggested.
Frequency
United States
The exact prevalence of plateau iris is unknown. However, it has been reported to account for more than 50% of patients younger than 60 years with recurrent angle closure. 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 is found in about one third of primary angle-closure glaucoma suspects after laser iridotomy.
Mortality/Morbidity
Plateau iris is an important cause of angle-closure glaucoma in patients younger than 50 years.
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.
Glaucoma, Intraocular Tumors
Other Problems to be Considered
Pseudoplateau iris: In pseudoplateau iris, the anterior displacement of the peripheral iris is not caused by an enlarged or anteriorly positioned ciliary body. Cysts of the iris and/or ciliary body neuroepithelium most often are responsible. This condition is distinguished easily from plateau iris because the angle usually is closed in only one quadrant or, if cysts are multiple, at several focal loculations. Ultrasound biomicroscopy is extremely helpful in identifying the underlying mechanism responsible for pseudoplateau iris.
Ciliary body cyst
Iris cyst
Peripheral anterior synechiae
Incomplete iridotomy
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.
- Any element of pupillary block also may be confirmed with ultrasound biomicroscopy (UBM) imaging.
- Optical coherence tomography (OCT) has evolving utility in imaging anterior segment structures and may assist in diagnosing plateau iris.
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.
- 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. 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.
- 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.1
- If angle closure persists despite iridotomy and sufficient peripheral laser iridoplasty, surgical intervention in the form of goniosynechialysis, trabeculectomy, or tube-shunt implantation surgery may be needed to allow bypass of aqueous flow and to control IOP.
Consultations
Consultation and/or comanagement with a glaucoma specialist may be helpful in patients who fail to respond to laser iridotomy and iridoplasty.
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.
Drug Category: Miotics
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.
| Drug Name | Pilocarpine (Pilocar, Piloptic, Pilostat, Akarpine, Ocusert Pilo-40) |
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| Description | 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. |
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| Adult Dose | Solution: 1 or 2 gtt tid/qid
Gel: 0.5-inch ribbon in lower conjunctival sac of affected eye(s) qhs
Ocusert Pilo-20 or 40: Insert pledget in inferior palpebral fornix weekly |
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| Pediatric Dose | Not established |
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| Contraindications | Documented hypersensitivity; acute inflammatory disease of anterior chamber; peripheral retinal disease |
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| Interactions | May be ineffective when used concomitantly with nonsteroidal anti-inflammatory agents |
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| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
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| Precautions | Caution in acute cardiac failure, peptic ulcer, hyperthyroidism, GI spasm, bronchial asthma, Parkinson disease, recent MI, urinary tract obstruction, and hypertension or hypotension |
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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
Medical/Legal Pitfalls
- Patients must be informed that this is a chronic condition that may recur despite initial treatment success. Regular follow-up examinations need to be emphasized as well as the risk of future development of glaucoma.
| Media file 1:
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. |
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Media type: Image
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| Media file 2:
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. |
 | View Full Size Image | |
Media type: Image
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Glaucoma, Plateau Iris excerpt Article Last Updated: Feb 11, 2008
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