Eyes on the primary angle-closure spectrum tend to have a small, “crowded” anterior segment and short axial length (AL). The most important factors predisposing an eye to angle closure are a shallow anterior chamber, a thick lens, increased anterior curvature of the lens, a short AL, and a small corneal diameter and radius of curvature. Studies using anterior segment imaging have contributed additional parameters that are risk factors for angle closure, including increased iris thickness and area and greater lens vault (see the discussion in Chapter 4 on anterior segment imaging). An ACD of <2.5 mm predisposes patients to PAC; in most patients with PAC, the ACD is <2.1 mm. Improvements in ocular biometry techniques have allowed researchers to demonstrate a clear association between ACD and development of PAS. While primary PAS seem to be uncommon in eyes with ACD >2.4 mm, there is a strong correlation between increasing PAS formation and an ACD of <2.4 mm. However, in some cases, angle closure can occur in eyes with deep anterior chambers, with plateau iris as a common cause.
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.