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
Mammalian eye a smaller, more sharply curved one and a larger lesser curved sphere. The former, the anterior segment is the front sixth of the eye that includes the structures in front of the vitreous humour: the cornea, iris, ciliary body, and lens. Within the anterior segment are two fluid-filled spaces: Aqueous humor fills these spaces within the anterior segment and provides nutrients to the surrounding structures. Some ophthalmologists specialize in the treatment and management of anterior segment disorders and diseases. The posterior segment is the back five-sixths of the eye that includes the anterior hyaloid membrane and all of the optical