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
Sensory root of ciliary ganglion Sensory root of ciliary ganglion Sensory fibers from the eyeball (the cornea, iris, and ciliary body) run posteriorly through the short ciliary nerves and pass through the ciliary ganglion without forming synapses. They leave the ciliary ganglion in the sensory root of ciliary ganglion, which joins the nasociliary nerve—a branch of the ophthalmic nerve. From there, the signal travels back through the ophthalmic nerve to the trigeminal nerve and back into specific nuclei in the thalamus where they are relayed to areas in the cerebral cortex. The exact distribution of sensory fibers, like the distribution of sympathetic fibers, is anatomically