The anterior chamber is bounded anteriorly by the corneal endothelium; posteriorly by the anterior surface of the iris, ciliary body, and pupillary portion of the lens; and peripherally by the trabecular meshwork (Fig 7-1). The normal central depth of the anterior chamber is approximately 3.0–3.5 mm. The trabecular meshwork is derived predominantly from the neural crest.
The histologic features of the anterior chamber angle correlate with its gonioscopic landmarks (Fig 7-2). For example, the termination of Descemet membrane manifests gonioscopically as the Schwalbe line. The scleral spur, a triangular extension of the sclera that appears gonioscopically as a white band, can be identified histologically by tracing the outermost longitudinal ciliary muscle fibers to its insertion. Anterior to the scleral spur in an internal indentation of the sclera is the trabecular meshwork and Schlemm canal. On gonioscopy, the posterior trabecular meshwork appears more pigmented than the rest of the meshwork because of its increased thickness. The meshwork is lined with cells that appear flat and have slender spindle-shaped nuclei known as trabeculocytes. These cells function to phagocytose material from the aqueous humor and have contractile properties.
See Figures 2-13 and 2-23 in BCSC Section 2, Fundamentals and Principles of Ophthalmology, which includes additional images and discussion of the structure and physiology of the anterior chamber and trabecular meshwork.
Figure 7-1 The normal anterior chamber angle, the site of drainage for the major portion of the aqueous humor flow, is defined by the anterior border of the iris, the pupillary zone of the anterior lens capsule, the face of the ciliary body, the internal surface of the trabecular meshwork, and the posterior surface of the cornea.
(Courtesy of Nasreen A. Syed, MD.)
Figure 7-2 Gonioscopic landmarks of a normal anterior chamber angle with histologic correlation. TM = trabecular meshwork.
(Courtesy of Tatyana Milman, MD.)
Excerpted from BCSC 2020-2021 series: Section 4 - Ophthalmic Pathology and Intraocular Tumors. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.