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
Vitreous body wide array of proteins. Despite having little solid matter, the fluid is substantial enough to fill the eye and give it its spherical shape. The lens, on the other hand, is tightly packed with cells. The vitreous humour has a viscosity two to four times that of water, giving it a gelatinous consistency. It has a refractive index of 1.336. The vitreous fluid is not present at birth (the eye being filled with only the gel-like vitreous "body"), but found after age 4-5, and increases in size thereafter. Produced by cells in the non-pigmented portion of the ciliary body, the