|LETTER TO THE EDITOR
|Year : 2016 | Volume
| Issue : 3 | Page : 194-195
Plateau iris: An important anatomical configuration not to miss
Haitham Hilal Al Mahrouqi, Ali Alsheikheh
Department of Ophthalmology, Al Nahdha Hospital, Muscat, Oman
|Date of Web Publication||14-Oct-2016|
Haitham Hilal Al Mahrouqi
Department of Ophthalmology, Al Nahdha Hospital, P.O. Box: 937, Postal Code 112, Ruwi, Muscat
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Al Mahrouqi HH, Alsheikheh A. Plateau iris: An important anatomical configuration not to miss
. Oman J Ophthalmol 2016;9:194-5
The term plateau iris was first coined by Tornquist in 1958 to describe the iris configuration of a young female with high intraocular pressure (IOP) and flat iris surface. 
Wand et al. in 1977  classified plateau iris into plateau iris configuration (PIC), a preoperative diagnosis, in which the iris is anteriorly displaced compromising the iridocorneal angle resultin&g in angle closure glaucoma, but often resolves with peripheral iridectomy and plateau iris syndrome (PIS), a postoperative diagnosis where angle closure is observed with PIC, despite eliminating the pupillary block mechanism with patent peripheral iridectomies.
Plateau iris is now regarded as one of the basic three mechanisms, which result in primary angle closure glaucoma, namely, pupillary block, plateau iris, and phacomorphic. 
Gonioscopy often reveals double hump sign, and ultrasound biomicroscopy (UBM) shows anterior positioning of the iris root.
The diagnosis and effective treatment of plateau iris is often delayed in clinical practice, which results in irreversible glaucomatous optic nerve damage. We report a case of PIS, in which the management was delayed.
A 48-year-old man without any previous medical was referred to our tertiary eye hospital for surgical management of refractory angle closure glaucoma with high IOP in the left eye, despite having three patent peripheral iridotomies and being on timolol 0.5% b.i.d, brimonidine tartrate 0.2% b.i.d, and latanoprost 0.005% nocte.
This patient initially presented to the referring hospital with an episode of left eye acute angle closure glaucoma, which was effectively controlled initially with topical medications and neodymium-doped yttrium aluminum garnet (Nd-Yag) peripheral iridotomy for this eye (and prophylactic peripheral iridotomy for the right eye). In the subsequent two months, he presented twice to the same hospital with increased IOP (40 mmHg and 38 mmHg) which was unresponsive to further peripheral iridotomy and medical therapy. Thus, he was referred to our service for possible surgical management.
Ocular examination of the right eye (RE) revealed best-corrected visual acuity (BCVA) of 6/9, corrected IOP of 17 mmHg without treatment, shallow anterior chamber (AC) in the periphery with a patent peripheral iridotomy, and a healthy optic disc. The left eye (LE) examination revealed BCVA of 6/12, corrected IOP of 38 mmHg with the above-mentioned treatment, shallow AC with three patent peripheral iridotomies, and advanced cupping (cup-to-disc ratio of 0.9). Gonioscopy with Zeiss lens showed RE Shaffer Grade 2 angles and LE Shaffer Grades 1-2 angles in spite of patent peripheral iridotomies in both eyes. The angles open widely with indentation. There was also double hump sign [Figure 1] and an absence of peripheral anterior synechiae.
Visual fields and optical coherence tomography were performed, which showed tunnel vision in the left eye [Figure 2] and thinning of the superior and inferior retinal nerve fiber layer. Unfortunately, UBM was not available in the hospital.
While in clinic, he was trialled on pilocarpine 2% for the left eye and IOP decreased to 17 mmHg. A diagnosis of PIC was made for the right eye and PIS for the left eye. The patient underwent peripheral iridoplasty using argon laser for the left eye on two different occasions (parameters: Spot size 300-500 μm, power 400 mw, and duration 50 ms). Gonioscopy on 2-week post peripheral iridoplasty showed Shaffer Grades 3-4 angles in the left eye and IOP was 14 mmHG. The patient was subsequently seen few times in clinic with a stable IOP on latanoprost and timolol for the left eye.
PIS is an important etiological differential of acute angle-closure glaucoma, especially where effective IOP control cannot be attained with peripheral iridotomies alone in the absence of other causes.
Our case was a middle-aged man with the left eye angle closure glaucoma where IOP was not adequately controlled with anti-glaucoma medications and peripheral iridotomies. Although referred from his local hospital for surgical management, he was found to have PIC in the right eye and PIS in the left eye. The IOP was effectively controlled initially with pilocarpine and later with peripheral iridoplasty and a lesser number of anti-glaucoma medications.
Plateau iris is characterized by a straight iris profile where the root is pushed forward due to the rotated and anteriorly positioned ciliary body, thus abutting the trabecular meshwork with potentially occludable angle.  It is thought that pupillary block often accompanies PIC, which exacerbates the problem. Thus, the initial management is often with a patent Nd-Yag peripheral iridotomy. 
Miotics such as pilocarpine stretches the iris and opens the angle. Such treatment can be used in temporary control, given its effects on decreasing vision in dim light, and others like myopic shift, uveitis and risk of retinal detachement. However, for permanent control, peripheral iridoplasty using argon laser is often advocated.  The 360° laser peripheral iridoplasty uses low energy which create fibrosis to retract the iris centripetally toward the pupil and prevent occlusion of the angle. Filtering surgery can be resorted to if medical and laser procedures fail to effectively control the IOP.
Although uncommon and may be difficult to diagnose, PIS is an important entity relating to acute angle closure. Early suspicion (especially where there is failure to effectively control IOP with peripheral iridotomy and medical therapy) and effective treatment prevent permanent glaucomatous optic nerve damage.
I would like to thank Dr. Abdulsattar Nasser for his contributions toward providing quality images.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Tornquist R. Angle-closure glaucoma in an eye with a plateau type of iris. Acta Ophthalmol (Copenh) 1958;36:419-23.
Wand M, Grant WM, Simmons RJ, Hutchinson BT. Plateau iris syndrome. Trans Sect Ophthalmol Am Acad Ophthalmol Otolaryngol 1977;83:122-30.
Stamper RL, Lieberman MF, Drake MV. Becker-Shaffer's Diagnosis and Therapy of the Glaucomas. 8 th
ed. China: Elsevier Inc.; 2009.
Ritch R, Tham CC, Lam DS. Long-term success of argon laser peripheral iridoplasty in the management of plateau iris syndrome. Ophthalmology 2004;111:104-8.
[Figure 1], [Figure 2]