Cornea is a transparent anatomic structure, non vascularized, rich in nerve endings and is the main optic component in the ocular system. It has five layers; the outer one, called epithelium, is composed of five or six layers of cells of different thickness.
Pupil is a hole through which light enters the eye. Light coming from the pupil, through the lens reaches the retina. Its size is important for eye surgery.
The lens is made of a small biconvex lens, with a thickness of about 3,6mm. Its function is to correct focal vergence when we focus on objects that are placed at different distances from the eye.
The iris is a pigmented membrane, located behind the cornea and before the lens, it has a central hole (pupil). Its function is to manage light quantity that gets inside the eye.
Vitreous humor is located between the retina and the lens; it is composed of a transparent gelatinous substance and its function consists in keep the retina adherent to the pigmented epithelium.
Optic nerve links the eye to the brain, just like a cable connects a videocamera to the television. It is made of about two millions nervous fibers that can become less and less because of the time passing or diseases.
Macula is the most central portion of the retina and controls our ability to recognize objects and colors, to read or write, etc, It contains a very small area called central fovea: this is a highly specialized structure that is responsible, in case of very strong brightness, for the best possible visual acuity, color perception and contrast sensitivity. Inside the macula, 3 kinds of cones can be found and everyone is sensitive for a special wavelenght: red, green and blue. The colored images we see, come from the combination of stimula coming from the different cones. Cones are mostly located in the central fovea and in the adjacent retinal portion, where they are placed one next to the other.
Fovea is the central part of the macula, the most sensitive part of the retina. Is has no vessels but a high concentration of photoreceptors, especially cones.
Retina is a sensitive membrane, split in three portions: a pigmented layer, a vascular layer, a layer composed of nervous fibers and photoreceptors (6 millions cones and 120 retinal rods). When the focused image falls onto the retina, a series of physical, chemical and electric events happen and, through the optic nerve, the information gets to the visual cortex, where it is corrected and elaborated.