- location: posterior aspect of the globe
- function: vascularization of the outer retina
- arterial supply: posterior ciliary arteries
- innervation: short ciliary nerves, long ciliary nerves
- relations: ciliary body anteriorly, optic nerve (II) posteriorly
The choroid is a pigmented, vascular layer, which represents the posterior part of the vascular tunic of the eye called the uvea. The function of the choroid is to provide oxygen and nutrients to the outer layers of the retina . It is delineated from the anterior part of the uvea called the ciliary body at the ora serrata . The choroid has an opening for the optic nerve at its entry point into the posterior aspect of the globe.
It is supplied by the posterior ciliary branches of the ophthalmic artery and drained by the vorticose veins into the ophthalmic veins . Sympathetic innervation to the choroid from the superior cervical ganglion is carried via the long ciliary nerves. It also receives parasympathetic innervation from the pterygopalatine ganglion via the short ciliary nerves, however, these also carry parasympathetic fibers from the ciliary ganglion .
The choroid is described as having four microscopic layers .
From superficial to deep:
- large vessel layer
- intermediate-sized vessel layer
- choriocapillaris comprised of capillaries
- Bruch’s membrane, which is the basement membrane of the choroid