The choroid is the pigmented vascular tissue that forms the middle coat of the posterior part of the eye. It extends from the ora serrata anteriorly to the optic nerve posteriorly and consists of 3 principal layers:
lamina fusca—outermost, pigmented layer with fine attachments to the sclera
stroma—central layer of loose fibrovascular connective tissue with arterioles originating from the short posterior ciliary arteries and veins draining to the vortex veins
choriocapillaris—innermost layer containing thin-walled capillaries that are contiguous with Bruch membrane
Figure 12-4 Normal choroid. The choroid is a vascular, pigmented structure located between the retinal pigment epithelium (RPE) and the sclera. The layer closest to the RPE is composed of capillaries and is known as the choriocapillaris (arrowheads). The lamina fusca is also shown (asterisks) (hematoxylin-eosin [H&E] stain).
(Courtesy of Nasreen A. Syed, MD.)
The choriocapillaris is the blood supply for the retinal pigment epithelium (RPE) and the outer retinal layers (Fig 12-4). In addition to blood vessels, the choroid contains melanocytes, fibrocytes, nerves (eg, long posterior ciliary nerve), and various inflammatory cells. See BCSC Section 2, Fundamentals and Principles of Ophthalmology, for more information on the uveal tract.
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.