EYES and their functions

 

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.

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 form 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 transmit. 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 themacula. The Macula is a highly sensitive part of the retina. It is responsible for our detailed vision. The center of the macula is called thefovea which has a major role in detailed perception. When there is damage to the macula, we are unable to see finer details.

FUN FACTS

• The human eye blinks an average of 4,200,000 times a year.
• It's impossible to sneeze with your eyes open.
• Our eyes are always the same size from birth, but our nose and ears never stop growing.
• Our body has some natural protection for our eyes. Our eyelashes help to keep dirt out of our eyes. Our eyebrows are made to keep sweat from running into our eyes.
• The shark cornea has been used in eye surgery, since its cornea is similar to a human cornea.
• The number one cause of blindness in adults is diabetes.
• The eyeball of a human weighs approximately 28 grams.
• The eye of a human can distinguish 500 shades of the gray.
• The cornea is the only living tissue in the human body that does not contain any blood vessels
• People generally read 25% slower from a computer screen compared to paper.
• Men are able to read fine print better than women can.
• All babies are colour blind when they are born.
• Babies' eyes do not produce tears until the baby is approximately six to eight weeks old.