Eyes

Eyes
User's Manual
Amazing Facts
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Sight

There are more brain cells devoted to sight than to any other sense. Sight represents 3/4 of our perception of the world. Your eyes and ears allow you to thoroughly evaluate your environment at a distance. Using your eyes, you can recognize faces, interpret art, read literature, avoid danger, express yourself and gaze at the wonders of nature. Your eyes also provide visual references, such as the horizon, to enhance your sense of balance.

Eye Balls

Your eyes are two jelly-filled balls nestled within fat and protected by the surrounding bony skull. They are very similar in design to a camera. The eyelid represents the protective lens cap. A clear membrane, called the conjunctiva, covers the visible front of the eye and is continuous with the inside surface of the eyelid. The cornea encloses the lens within a nutrient rich fluid, representing the glass protecting the inner lens of a camera. The colorful iris represents the aperture, which controls the amount of light that reaches the lens. The lens is a gelatinous disk that focuses the light on the back of the eye. The retina represents the film of a camera. However this is no ordinary film. It can be exposed 10 times per second to continuously capture images from the environment around you. This retina, composed of millions of receptors, sends electrical signals to the brain where the signals are processed into images and memory as a digital camera processes and stores images on a disk.

Tears

A mixture of salt and water. Tears clean the eye of debris, prevent the eyes from drying out and provide lubrication allowing the eyes to constantly and comfortably move. Tears are produced in the tear glands, flow across the eye and empty into the lacrimal duct. When we cry, we excrete more tears than normal. This causes the lacrimal duct to overflow requiring some of the tears to flow down our cheek. Tears from the lacrimal duct drain into the nose, which explains why we sniffle when we cry. The large amount of tears flowing through our lacrimal duct flows right through our nose and out the nostrils, dragging mucous with it. Some of the tears might flow down the back of the nasal cavity and into the throat, giving us a salty taste when we cry.

Why do we cry?

Crying is a natural reflex that begins as soon as a baby is born. It's a necessary expressive act including loud vocalizations, tears and certain facial expressions. A baby will cry, because it needs something or because crying is its only known form of expression. Crying alerts the mother to the baby's needs. It causes the mother to pick the baby up and hold it, thus keeping the baby warm, and forming an emotional bond between the mother and infant. If the baby's crying continues it causes people to investigate what the baby needs and to fill those needs, whether the baby is hungry and needs to breast feed, or lacking stimulation and needs visual interaction to aid brain development. In this way the natural reflex of crying acts as a survival tool to ensure that the baby has the support it needs while it's still dependant on others to survive. In adulthood the natural reflex of crying remains as a way to alarm others and as a powerful manner of expression. We cry when we feel emotional or physical pain or when we're extremely happy. When we are hurt physically, it alerts others to come to our aid. When we are affected emotionally, it lets others know of the consequences of their actions or once again alerts others to come to our aid. It also gives us a way of releasing stress, by forcing us to face the discomfort we're feeling. In these ways crying continues to act as a survival tool.

User's Manual

When participating in outdoor activities that subject your eyes to bright sunlight, wear ultraviolet protective sunglasses. Activities involving snow and water such as fishing, skiing, snowboarding, lifeguarding, etc. subject your retinas to high levels of reflected ultraviolet radiation. Wearing good quality sunglasses will protect your eyes and protect you from making a mistake due to poor visibility and thus injuring some other part of your body.

Important: You should not wear sunglasses or tinted glasses on a regular basis throughout the day. It's good to block long exposure to ultraviolet rays. But during the rest of the day, you need light for your body to function normally. The pineal gland, which helps regulate metabolism, behavior, and your physiology is controlled by light. Parts of your brain are controlled by periods of light and darkness throughout each day to regulate your system and sleeping behavior. So don't wear sunglasses all day. Only wear them when needed and don't wear them at night, Silly, or you will trip and fall.

If you wear contacts
Do not leave them in your eyes over night no matter what type they are. You can cause infection and damage the cornea. An eye infection left untreated can eventually cause blindness. Be careful with those finger nails when taking out your contacts also.

Eye Strain
Some tasks, such as working at a computer, reading a book, building a model, or completing a detailed drawing, can strain the eyes if done for long periods of time. During these activities the eyes are required to focus intensely at close range. It's like sitting in a fixed position with your head hanging over a book for hours at a time, causing the neck and back muscles to become strained. Like other muscles in your body, your eye muscles are used to constant movement. If limited to a specific position, they can also become strained. Working at a computer every day can cause eyestrain, headaches, blurred vision, dryness, irritation, sensitivity to light, double vision and after images. When performing these tasks make sure to take periodic breaks, by looking up and focussing on objects of varied distances around the room. Operating under low levels of light can also strain the eyes.

Avoiding Injury
When participating in activities that put your eyes at risk for injury due to projectiles or flying debris, always use safety goggles.

Wear your safety goggles in chemistry lab when dealing with eye irritants or chemicals that may cause damage if splashed into the eyes. In the case of emergency immediately flush the eye with clean water.
When exposing the eyes to chlorine, such as during water polo, milk is effective at flushing the chlorine out of the eyes.
When working with wood or metal, always wear safety goggles.
When playing racquetball, always wear safety goggles.

Effects of Drugs
Aspirin, Marijuana, and other drugs such as Tetracycline can cause damage to the eyes. So as usual always take over-the-counter-medication as indicated in the directions. Avoid illegal drugs. And only use prescribed drugs for the illness they were prescribed for, and only according to the instructions given by your doctor.

Nutrition

A well balanced diet with plenty of fresh fruits and vegetables (especially yellow and yellow orange foods such as carrots, yams, and cantaloupes) can keep your eyes healthy.

Fresh fruits and veggies provide the vitamins (A, B, C, and E) and minerals (selenium and zinc) needed for your eyes to remain healthy.

Fresh carrot juice is excellent for your eyes.

Broccoli, carrots, cauliflower, squash and sunflower seeds are good for your eyes.

Egg yolks, fish, lamb, lima beans, meats, mushrooms, pecans, poultry and sunflower seeds will provide zinc, which may help reduce vision loss. (Never take over 100 mg of zinc daily.)

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Amazing Facts

  • The retina captures 10 images per second throughout its working life.
  • Eyes at birth are 2/3 their mature size.
  • One out of every 20 people is colorblind.
  • One out of every 12 men is colorblind.
  • There are 6 to 7 million cones (color light receptors) and 120 to 125 million rods (black and white receptors) in each eye.
  • Pupils are holes through which the dark interior of the eye can be seen.
  • Blinking causes the eyes to be closed for a total of one hour each day.
  • Tears enter tiny holes on the inside corner of the eye, travel down the lachrymal duct and into the nose causing you to sniffle when you cry, or to sniffle when cold wind causes more lubrication of the eye.

Related Links

Nervous System
Brain

Ears
Nose
Tongue