Choroid Choroid The choroid, also known as the choroidea or choroid coat, is the vascular layer of the eye, containing connective tissues, and lying between the retina and the sclera. The human choroid is thickest at the far extreme rear of the eye (at 0.2 mm), while in the outlying areas it narrows to 0.1 mm. The choroid provides oxygen and nourishment to the outer layers of the retina. Along with the ciliary body and iris, the choroid forms the uveal tract. The structure of the choroid is generally divided into four layers (classified in order of furthest away from the
Long ciliary nerves Long ciliary nerves The long ciliary nerves, two or three in number, are given off from the nasociliary nerve as it crosses the optic nerve. The nasociliary nerve that the long ciliary nerves branch from is itself a branch of the ophthalmic branch (V) of the trigeminal nerve (CN V). They accompany the short ciliary nerves from the ciliary ganglion, pierce the posterior part of the sclera, and running forward between it and the choroid, are distributed to the iris and cornea. The long ciliary nerves provide sensory innervation to the eyeball, including the cornea. In addition, they contain sympathetic