Plateau Iris

Plateau Iris

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Chief Complaint: Referral for evaluation of glaucoma

History of Present Illness: A healthy 47-year-old female with no family history of glaucoma was referred for possible glaucoma. She denied any visual complaints.

Past Ocular History: Hyperopia and presbyopia

Medical History: Iron deficiency anemia secondary to uterine fibroid

Ocular Examination

Visual acuity with correction

• OD: 20/20-1
• OS: 20/20

MRx

• OD: +2.50 +0.25 x086
• OS: +2.75 +0.25 x004

Pupils: symmetric, briskly reactive and there is no relative afferent pupillary defect OU

Visual Fields: full by confrontation OU

Intraocular Pressure by Applanation Tonometry

• OD: 11 mm Hg; pachymetry 541 micrometers
• OS: 13 mm Hg; pachymetry 543 micrometers

Anterior Segment Examination:

Conjunctiva: normal

Cornea: clear without Kruckenberg spindle or endothelial changes

Iris: normal architecture without heterochromia or transillumination defects

Anterior chamber: narrow angles by Van Herrick

Lens: Clear OU

Gonioscopy (Spaeth classification):

• OD: Temporal (B) C 30P+1 Nasal (B) C 30P+1 Superior (B) C 30P+1 Inferior (B) C 30P+1
• OS: Temporal (B) C 20P+1 Nasal (B) C20P+1 Superior (B) C 20P+1 Inferior (B) C 30P+1

Figure 1: View through Goldmann 3 mirror. The iris drapes over the ciliary body producing the characteristic "sine wave" or double-hump

Alternative link to video (wmv file, approx 3.5 MB)

Video: first note the anterior chamber is shallow by Van Herrick. On indentation gonioscopy, the "double hump" is observed

Figures 2 and 3: Anterior Segment OCT

Figure 2: Anterior Segment OCT: Pre-Laser peripheral iridotomy (LPI)

Figure 3: Anterior Segment OCT: Post-LPI, note widening of the angle

Figure 4: Ultrasound biomicroscopy: The anterior position of the ciliary body pushes the peripheral iris against the trabecular meshwork

Course

This patient was initially treated with LPIs in each eye. Her angle depth improved in each eye but there was concern that the angle in the left eye was still occludable. She underwent a laser iridoplasty OS without complication and repeat gonioscopy demonstrated improvement in the angle depth OS. At present, the angle in the right eye does not appear to be occludable and we are monitoring her with repeat gonioscopy exams every 6 months.

Discussion

Plateau iris syndrome is a relatively uncommon form of primary angle closure glaucoma that is seen more often in younger adults than pupillary block angle-closure glaucoma. It is caused by large or anteriorly positioned ciliary processes that push the peripheral iris forward. The mechanical position of the ciliary processes against the trabecular meshwork crowds the angle and obstructs aqueous outflow. A component of pupillary block is often present.

The central anterior chamber may appear to be of normal depth on slit lamp examination. On examination with gonioscopy, the iridocorneal angle is usually crowded or even closed. The iris typically appears to have a flat approach (on a plane to intersect Schwalbe's line) with a steep drop-off just before the trabecular meshwork. On indentation gonioscopy the "sine wave" or "double-hump sign" is seen. The peripheral "hump" is created by the iris draping over the ciliary body and the more central hump by the iris curving over the anterior lens surface.

Ancillary imaging modalities can be helpful in making the diagnosis of plateau iris. Ultrasound biomicroscopy can provide information of the anterior segment anatomy as well as help confirm any element of pupillary block. Anterior segment optical coherence tomography (OCT) can also provide insight into the anatomy, but it is not a dynamic examination and does not provide as much information as gonioscopy.

Treatment

Some element of pupillary block frequently exists in patients with plateau iris configuration and generally, peripheral laser iridotomy should be performed as the first intervention in patients suspected of having plateau iris. This often times is an adequate treatment for eyes with plateau iris configuration. However a subset of patients will have a persistent occludable angle despite a patent iridotomy causing plateau iris syndrome. Eyes where the iridocorneal angle has persistent apposition or the intraocular pressure remains elevated should be treated with laser iridoplasty. The goal of laser iridoplasty is to place laser burns at the peripheral iris to shrink the iris and pull it from the angle. Of course, if laser surgical treatment is ineffective in controlling the intraocular pressure, conventional surgical procedures such as a trabeculectomy or a tube-shunt may need to be implemented.

Laser settings recommended by Wallace L.M. Alward, MD in Glaucoma: The Requisites in Ophthalmology.

Laser Iridotomy

• Argon Laser Peripheral Iridotomy:
• Spot size: 50 micrometers
• Duration: 0.02-0.2 seconds
• Power: 1 Watt
• Lens: Abraham or Wise

Nd:Yag Laser Peripheral Iridotomy

• Spot size: fixed
• Duration: fixed
• Energy: 1-12 mJoules
• Lens: Abraham or Wise

Argon Laser Iridoplasty

• Spot size; 200-500 micrometers
• Duration: 0.2-0.5 seconds
• Power 150-300 mWatt
• Lens: none or Goldmann 3 mirror
  • Note: larger spot size and longer duration

Diagnosis: Plateau Iris Syndrome

Differential Diagnosis

• "Pseudo plateau iris" caused by iris cysts or ciliary body cysts
• Primary angle closure
• Pupillary block
• Peripheral anterior synechiae

EPIDEMIOLOGY Exact incidence is not well known Diagnosis should be suspected when angle closure occurs in patient who is young or myopic and when angle narrowing persists despite iridotomy Generally occurs in younger age group vs. primary pupillary block glaucoma. Average age 30-50s Slight female and hyperopic preponderance	SIGNS Narrowed or closed angle with iris on a plane to intersect with Schwalbe's line then with a sharp drop-off of the peripheral iris Indentation gonioscopy reveals the "double-hump" sign
SYMPTOMS May present with angle closure, either spontaneously or after pupillary dilation More commonly, patients are asymptomatic and the diagnosis is made on routine examination	TREATMENT Often an element of pupillary block exists so laser peripheral iridectomy is indicated If not improvement in appearance of the angle laser iridoplasty to contract the peripheral, pulling the iris away from the crowded angle