The eye is made up of a variety of tissues. From front to back, at the top is a clear layer of tissue called the cornea, which is devoid of blood vessels and therefore looks transparent. Further back is the dark gray or black iris, and in the middle of the iris is a hole that looks a little darker, called the pupil. Behind the pupil is the lens, and older people get cataracts because of clouding of the lens. Behind the pupil is the lens. Older people get cataracts because of clouding of the lens. Behind the pupil is the lens, and behind that is a very large cavity called the vitreous cavity, which contains the vitreous humor, a jelly-like fluid that cushions the eye from external impacts and protects the retina at the bottom of the eye. Behind the vitreous body is the retinal tissue, which is the nerve tissue of the eye that produces images and generates vision. The eye, from front to back, is made up primarily of these tissues.