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