Primary angle closure glaucoma (PACG) is a significant cause of visual disability worldwide. It predominantly affects the Eastern and South Asian population of the world. Early detection of anatomically narrow angles is important, and the subsequent prevention of visual loss from PACG depends on an accurate assessment of the anterior chamber angle (ACA). Gonioscopy has given way to modern day imaging technologies such as ultrasound biomicroscopy (UBM) and more recently, anterior segment optical coherence tomography (AS-OCT). Ultrasound biomicroscopy provides objective, high-resolution images of anterior segment anatomy, including the cornea, iris, anterior chamber, anterior chamber angle, and ciliary body. Optical coherence tomography (OCT) is a noncontact optical signal acquisition and processing device that provides magnified, high-resolution cross-sectional images of ocular tissues. Recent technological advances towards three-dimensional visualization broadened the scope of AS-OCT in ophthalmologic evaluation. Optical coherence tomography systems use low-coherence, near-infrared light to provide detailed images of anterior segment structures at resolutions exceeding that of UBM. This paper summarizes the clinical application of UBM and OCT for assessment of anterior segment in glaucoma. 1. Introduction Primary angle closure glaucoma (PACG) is a leading cause of blindness worldwide [1]. It is potentially preventable if diagnosed early in the course of the disease, before irreversible damage has occurred to the optic nerve or trabecular meshwork (TM). Primary angle closure glaucoma comprises about 10% of glaucoma patients in the USA, and its prevalence varies amongst ethnic and racial groups [2]. Narrow angles are found in about 2% of Caucasians, with 0.1% having acute angle closure glaucoma [3–5]. The ethnic group in which PACG is most common is Eskimos [6]. Angle-closure is less common in blacks but more likely to develop chronic ACG when they do develop the disease [7–9]. Asians are prone to chronic angle-closure and often do not reach clinical attention until severe ocular damage has already occurred. In Asians, specifically, the incidence of angle-closure glaucoma outnumbers open-angle glaucoma [10]. In all racial and ethnic populations, ACG is found 3-4 times more often in females than males [11]. Finally, ACG is most prevalent in hyperopic and elderly patients, peaking between ages 55 and 70, since the anterior chamber depth and volume decrease with age due to nuclear sclerosis and in patients with a family history of angle-closure glaucoma
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