Knowing about your eye

The eye is one of the most complex organs in the body. Responsible for taking light signals to the brain, it functions as a natural camera that is an extension of the brain. It has several layers that are equivalent to the lens of the camera, the lens Diaphragm, the film, and the lens cover.


Cornea
Like the glass on a watch, the cornea is the clear protective coating on the front of the eye that allows light to pass through it without distortion. It also has a focusing function but unlike the lens cannot normally change its shape. It must thus be clear and regularly shaped to give good vision.

Iris
The Iris lies behind the Cornea and is colored imparting the so called color to the eye. The space between the Cornea and the Iris is called the Anterior Chamber and filled with a clear liquid the Aqueous Humor.

Pupil
There is a small hole in the iris called the Pupil seen as the black portion in the centre of the eye. The pupil decides how much light is need for the eye to see properly. It changes sizes to adjust for changes in light. It acts like the Aperture of a camera.

Conjunctiva
The conjunctiva is the clear covering (like cellophane) of the white part of the eye, the sclera.

Sclera
The sclera is the "white" part of the eye and is like the light impermeable case of a camera.

Lens
Every camera must have a lens to properly focus the picture. Your eye has a lens, too, which lies directly behind the pupil. Your lens is normally clear and transparent. The lens of the eye focuses the images transmitted through the cornea to the retina which acts as the film that records the picture. The picture is then transmitted by the optic nerve to the brain, where the image is interpreted. It's the brain that does the actual seeing.

Retina
The retina is the light-sensitive part of the eye. It has one major artery and one major vein, which are called the central retinal artery and vein respectively.

Uvea
The uvea is the middle section of the eye. It has three parts: the iris (the colored part of the eye), the ciliary body and the choroid. The Iris acts like the aperture of the camera. The Ciliary body produces the Aqueous humor for maintaining the shape and pressure of the eye and the Choroid supplies some part of the nutrition to the Retina.

Macula
The macula is a part of the Retina that contains special light-sensitive cells which allows us to see fine details clearly. The macula is an important part of the eye because even small changes can cause severe vision loss.

Vitreous
The vitreous is the clear jelly-like substance that fills the middle part of the eye between the lens and retina.

Optic Nerve
The optic nerve is the pathway that connects the eye to the brain. It is the means through which images captured by the retina reach the brain, where those images are interpreted.

Eyelids
The lids of each eye is like the lens hood of a camera. They are vital to the preservation of sight. They maintain vision by keeping moisture inside, and foreign particles outside of the eye. Without eyelids, our eyes would quickly dry out from exposure to air, or could be damaged severely by a cinder, pebble, or some other foreign object. Think of how fast you blink when something approaches your eye.

The Lacrimal System
The lacrimal (tear) system is a miniature drainage network, which prevents tears from continuously rolling down the cheeks. From the surface of the eye, the tears flow along the edge of the lids toward the nose. Just before reaching the corner of the eye, the tears slide into two tiny drain tubes, and then into a larger tube which carries the tears into the Lacrimal Sac. This sac is tern connected to the nose through a tube known as Naso-Lacrimal Duct This explains why crying often causes one to blow one's nose.

The Orbit
The orbit is the bony housing in which the eyeball sits. If you place your finger on your brow and press down, you will feel the edge of the orbit. By continuing to move your finger around in a circle, you can feel the orbit protection provided the eyeball on all sides, except in the front where the lids protect the eye. Between the bony housing and the eyeball are other structures such as fat, muscle, blood vessels and glands. These are known as the orbital contents.