The human eye is an organ which reacts to light and pressure. As a sense organ, the mammalian eye allows vision. ... Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth.
a human eye has the following main parts :

Cornea : it is the transparent spherical membrane covering the front of the eye.
Crystalline Lens : the eye lens is a convex lens made of a transparent, spherical, soft membrane.
Iris : it is a dark muscular diaphragm between the cornea and the lens. it controls the size of the pupil.
Pupil : it is a small hole between the iris through which light enters the eye
Ciliary muscle : they hold the lens in position and help in modifying the curvature of lens.
Retina : image is form on the retina.
Optic nerve : it sends visual information from the retina to the brain.
Blind spot : it is the point where the optic nerve leaves the eye.
Aqueous Humour : it gives nutrition to the eye.