<Tr> <Th> FMA </Th> <Td> 58298 </Td> </Tr> <Tr> <Td_colspan="2"> Anatomical terminology (edit on Wikidata) </Td> </Tr> <P> 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 . </P> <P> The structure of the choroid is generally divided into four layers (classified in order of furthest away from the retina to closest): </P>

What is the function of the choroid layer