Eye Anatomy
How the Eye Works
The eye is an intricate part of our body. In comparison to a car, the engine being the heart, the gas tank being the stomach, the eye would be all the windows and gauges. Imagine having all the windows fogged and not being able to see. Imagine the gauges do not work and you do not know how fast you are going or how much gas is left in tank. You would have to drive with feeling only. Without the eye you would be in the same sinking boat. The eye allows you to not only view objects, but to view depth, color, size, and every little detail. The eye is a complicated machine in itself with many parts. The eye works by refracting light rays to the retina. The light rays are adjusted through muscles and certain parts to create the right amount of light refracted to the retina. When light arrives at the retina it is converted to both chemical and electrical energy before being sent through optic nerves to the brain. In the retina, millions of rods containing rhodopsin that are responsible for night vision and convert the light into electrical impulses sent to the brain. The retina also contains millions of cones that contain iodopsin that are used for bright light vision, visual perception, and color perception. Light is transformed here also and sent to the brain through optic nerves. The brain translates what it receives through optic nerves so that we understand what we see.
Parts of the Eye
Eye Anatomy consists of many intricate parts of the eye. It involves parts that allow light refraction, maintaining the shape of the eye, light conversion and much more. Although we will not list all of the parts we will try to explain some of them and their function.
Cornea
The cornea is the dome shape outer covering of the eye. It is like the windows of the car. It allows you to see but around you but protects you as well. The cornea is where most of the focusing of light occurs. It consists of many layers including the epithelium which is the tough outer layer that regenerates fairly quickly. The epithelium is usually removed or cut during many refractive procedures where the cornea is reshaped to focus light better.
Sclera
The Sclera is the outer white part of the eye that you can see. It provides protection and structure for the inner parts of the eye.
Conjunctiva and Lacrimal Glands
The conjunctiva is a mucus layer that keeps the eye moist. Infections to this area are known as the popular "Pink Eye." Lacrimal glands are found on the outer part of each eye and are producers of tears.
Vitreous Humor and Aqueous Humor
The Vitreous Humor is gel like substance in the back part of the eyeball which provides the shape of the eyeball. The Aqueous Humor is the watery region in the from of the eye ball. It is separated into two regions, the anterior chamber in front of the iris and the posterior chamber behind it. The canal of Schlemm drains water in this region and is sometimes blocked off leading to the disease known as glaucoma or other complications.
Sclera
The Sclera is the outer white part of the eye that you can see. It provides protection and structure for the inner parts of the eye.
Iris and Pupil
The Pupil is the dark, black circle of the eye. It contracts with brightness and expands during darkness allowing light to better transmitted. The iris is the colored part of the eye. This coloring is due to pigment cells in tissue in the iris. The iris contains the sphincter pupillae, a muscle used to narrow the pupil, and the dilator pupillae, a muscle used to widen the pupil.
Lens
The lens is a clear layer behind the pupil that does just what a regular lens does. The lens main purpose is to focus light by changing its shape. The ciliary body are muscles attached to the lens that help the lens change it shape to better focus light to the retina.
Retina
The retina is the inner most layer of sensitive tissue. When light is transmitted here images can clearly be transmitted to the brain. The retina consists of many layers including layers of rods and cones. Many cells in the retina transform light into chemical and electrical energy that is transferred to optic nerves. The back center of the retina contains the macula. The Macula is a highly sensitive part of the retina. It is responsible for our detailed vision. The center of the macula is called the fovea which has a major role in detailed perception. When there is damage to the macula, we are unable to see finer details.
These are some parts of the big machine we call the eye that is a small part of the even bigger machine we call the human body.
[Page updated 12/2010]
