The choroid is the part of the eye containing many blood vessels. It lies between the retina and the outside of the eye, (the sclera). It is an important part of the eye because, through the blood, it provides nourishment and oxygen to the part of the eye performing vision functions - the retina.
The choroid contains connective tissue and blood capillaries - very fine capillaries called choroicapillaries.
Edging the choroid is the bruch's membrane, the innermost part of the choroid. There is a subretinal space between the choroid and the retina. The bruch's membrane acts as a filter between the RPE (retinal pigment epithelium) and the choroicapillaries.