J Glaucoma Volume 20, Number 5, June/July 2011 R1 何元輝 2011/09/15 EBM discussion

 To determine the prevalence of plateau iris configurations in different group of glaucoma patients [ APAC, CACG, and OAG eyes ] ultrasound biomicroscopy.

 A flat iris plane accompanied by a narrow or closed anterior chamber angle. Relatively deep central chamber. The iris takes a flat approach towards Schwalbe's line. There is a prominent last roll of the iris before a steep drop-off into the chamber angle.

 In eyes with plateau iris configurations, ultrasound biomicroscopy (UBM) shows that ciliary processes are positioned adjacent to the posterior peripheral iris, thus closing the ciliary sulcus.

 Residual angle closure due to plateau iris configuration causes poor control of IOP, even after a pupillary block is relieved by laser or surgical iridotomy.

 APAC group : - unilateral headache, painful red eye, impaired vision, and nausea or vomiting, markedly elevated IOP (>35mm Hg) in an eye with a shallow anterior chamber. - Excluded : Patients with a closed angle, dilated pupil, corneal edema, or any other ocular disease that caused angle closure.

 CACG : - no history of APAC, - the posterior trabecular meshwork could not be seen for more than 180 degrees of the angle circumference without tilting the gonioscopic lens - indentation gonioscopy detected the presence of peripheral anterior synechiae (PAS) or appositional closure or iris stomal pigment deposition on the angle wall

 OAG: (control group) - van Herick grade 3 or 4, Scheie grade 0 or 1 - no PAS by gonioscopy, and  Eyes that had not undergone LPI were excluded from APAC and CACG groups.  Patients with a history of argon laser peripheral iridoplasty or any intraocular surgery, including cataract extraction, were excluded.

A quadrant that fulfilled all of the following criteria was defined as having a plateau iris configuration: (1) the ciliary process was anteriorly located, supporting the peripheral iris; (2) the iris root had a steep rise from its point of insertion, followed by a downward angulation from the angle wall; (3) the presence of a central flat iris plane; and (4) the presence of a closed ciliary sulcus (Fig. 2).

FIGURE 2. Images obtained from a patient in the open-angle glaucoma group (A) and acute primary angle-closure group (B).

 Quadrants that were considered to have a plateau iris configuration by 2 or 3 examiners were classified as having a plateau iris configuration. At least 2 quadrants needed to classify an eye to have Plateau iris configuration.

Gonioscopy showing an open angle (A), but a tilted view in the same eye (B) revealed that the iris root had a steep rise followed by a downward angulation.

 No statistically significant difference was observed among these groups.  The prevalence rate in the OAG group was higher than that expected  Similar prevalence in APAC and CACG.  UBM is an outstanding device for observing the angle of the eye, there is no general consensus regarding the diagnosis of plateau iris configurations using UBM.

 As no quantitative diagnostic criteria, the diagnosis of plateau iris configuration is somewhat subjective.

 The clinical significance of plateau iris configurations in OAG eyes is unclear.  OAG eyes do not have plateau iris configurations high enough to occlude the trabecular meshwork.

 Earlier studies using UBM reported that the superior quadrant was either the narrowest or the most common site of plateau configuration.  No significant difference in the prevalence of plateau iris configurations was observed among these groups in this study after an examination of each quadrant.  The clinical importance associated with the location of the plateau iris configuration (ie, quadrant) remains unclear.

 Because of the characteristics of the disease, the numb higher in the APAC group than in the other 2 groups.  An exact diagnosis of plateau iris configuration should have been made through a comparison of gonioscopic and UBM findings before and after pupil dilatation, which was not carried out.  The definition of plateau iris configuration did not completely fulfill this criterion.

 A longitudinal study including plateau iris heights should be conducted to investigate the clinical importance of plateau iris configurations.

 Thank you for your attention