Robert Ritch

Ultrasound Biomicroscopy in Plateau Iris Syndrome

Ultrasound biomicroscopy is a new technique that uses high-frequency ultrasound (50 to 100 MHz) to produce images of the entire anterior segment at high resolution (20 to 50 microns). The iridocorneal angle, iris, ciliary body, and posterior chamber can be imaged in detail and the dimensions and anatomic relationships of these structures determined. Plateau iris syndrome is a condition in which the angle remains appositionally closed or occludable after iridectomy for angle-closure glaucoma. How the iris remains in a position that allows it to occlude the angle has been uncertain. We performed ultrasound biomicroscopy eye examinations on eight patients with clinically diagnosed plateau iris syndrome. In all the patients, ciliary processes were situated anteriorly compared to the position in normal subjects and in patients with angle closure caused by pupillary block. The ciliary processes provide structural support beneath the peripheral iris, preventing the iris root from falling away from the trabecular meshwork after iridectomy.

Plateau Iris Is Caused by Abnormally Positioned Ciliary Processes

Plateau iris has been considered to be an anatomic variant of iris structure in which the iris root angulates sharply forward from its insertion point and then again angulates sharply centrally. The surface of the iris appears relatively flat, giving the iris the appearance of a plateau in sagittal section. The anatomic basis underlying plateau iris has thus far eluded definition. Indentation gonioscopy in eyes with plateau iris after iridectomy for angle-closure glaucoma reveals a different pattern of iris contour from that found in eyes with primary angle-closure on the basis of relative pupillary block. This configuration is consistent with abnormally large or anteriorly positioned ciliary processes pushing the peripheral iris anteriorly.

Pigment Dispersion Syndrome

P IGMENTARY GLAUCOMA WAS FIRST DESCRIBED as a distinct disorder in 1949 by Sugar and Barbour.1 They reported two young, myopic men with Krukenberg spindles, dense trabecular pigmentation, and open anterior chamber angles, whose intraocular pressure increased after mydriasis. Subsequently, the term pigmentary dispersion syndrome was applied to patients exhibiting the characteristic features without having elevated intraocular pressure. This term was finally changed to pigment dispersion syndrome, which is more syntactically correct.

A new lens for argon laser trabeculoplasty

Most ophthalmologists perform laser trabeculoplasty with a Goldmann three-mirror lens with an anti-reflective coating. The view of the superior angle, which is frequently narrower than the inferior angle, often presents difficulties in treatment. A lens has been devised which gives improved views of the superior portion of the angle. Plano-convex buttons provide magnification and increase resolution for difficult situations.