Function &Eye Structure :
The human eye is the organ which gives us the sense of sight. It is elegant in its detail and design and houses many structures that work together to facilitate normal vision.
Structures of the Eye
The orbit: The eyeball lies in a bony socket, known as the orbit. The orbit protects the eyeball. It is covered with fatty tissues which surround the eyeball and protect it from any external impact.
The Extra-ocular muscles: The eyes are attached to the wall of the orbit by six muscles, which help in the movement of the eyeball. These muscles are called extra-ocular muscles.
The Eyeball: The human eyeball is about 0.9 inches (24 mm) in diameter and is not perfectly round, being slightly ﬂat in the front and back. It is not a sphere but an oblate spheroid.
The Conjunctiva: The conjunctiva is a thin, translucent membrane that covers the outer surface of the eye and the inner surface of the eyelids. The glands in the conjunctiva produce tear ﬁlm that lubricates and protects the eye while it moves in its socket.
The Sclera: The sclera is the dense, white, ﬁbrous outer protective coat of the eye, commonly known as “the white of the eye”.
The Cornea: The cornea is a transparent avascular watch glass like structure forming anterior 1/6th of the outer ?brous coat of the eyeball. Light waves entering the eye are maximally bent and focused by the cornea, which is then fine-tuned by the lens of the eye.
The Iris: The iris is the coloured part of the eye and may be blue, green, gray, or brown. Depending on the amount of light in the external environment, iris can contract or relax to adjust the size of the pupil accordingly.
The ciliary body: The ciliary body is a tiny ring like structure present at the base of the iris. It changes the shape of the lens. It secretes aqueous humour, a fluid which provides nutrition to the eye.
The choroid: The choroid is a thin membrane lying beneath the scleroses. It absorbs light and prevents the light scattering.
The Lens: The lens is a clear, transparent body which is biconvex, semi-solid, and shaped like an elongated sphere. It is located just behind the iris & pupil. Its principal purpose is to fine-tune the focusing done by the cornea.
The Retina: The retina is a thin ﬁlm of tissue (like ﬁlm in a camera) where images are brought into focus. Cells of retina receive light and transform it into image-forming signals which are transmitted through the optic nerve to the brain.
The Optic nerve: The optic nerve is the nerve that transmits visual information (image signals-nerve impulses) from the retina to the brain.