When evaluating the anterior chamber, the examiner should note the uniformity of depth of the chamber. In the Van Herick method of estimating angle width, the examiner projects a narrow slit beam onto the cornea at approximately a 60° angle, just anterior to the limbus. However, the results can be misleading: this method is not sensitive enough to detect angle closure and is not a substitute for gonioscopy (discussed in detail in the Gonioscopy section).
Iris bombé and plateau iris syndrome can both result in an anterior chamber that is deep centrally and shallow or flat peripherally. In contrast, in malignant glaucoma and other forms of non–pupillary block angle closure with a posterior “pushing” mechanism, both the peripheral and central anterior chamber are shallow. In many circumstances, especially in the assessment of acute unilateral IOP elevation (when the cornea is often edematous, limiting the view of the anterior chamber and angle), examination of the fellow eye can provide useful information.
The anterior chamber is very deep and the iris configuration is often concave in pigment dispersion syndrome. In this condition, friction between the posteriorly bowed iris and the lens zonules causes pigment liberation from the iris epithelial cells.
The presence of white or red blood cells, circulating pigment, or inflammatory debris (such as fibrin) should be noted. The degree of inflammation (flare and cells) and presence of pigment should be determined before instillation of eyedrops.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.