Eye Spy: The Eye

Computer graphic of the human eye.

Parts of the Eye

  • Iris – The Iris is the colored part of the eye. Depending on genetics, people can have Irises that are blue, brown, green, or hazel. The Iris has attached muscles that will expand or shrink depending on how much light needs to enter the pupil in order to see.
  • Pupil – The Pupil is the black center of the eye. It is really a hole that allows light to enter through the eye. If it is very bright, the Pupil will be small, but if it is darker, the Pupil gets very large so that a large amount of light can get into the eye.
  • Cornea – The Cornea acts just like the lens of a camera. It is a clear film over the eye that helps put objects into focus.
  • Sclera – The Sclera is the white part of the eye. It is a dense layer that protects all the other parts of the eye.
  • Lens – In order to see things close up and then far away, the Lens bends light waves. This helps the cornea to focus on objects.
  • Retina – The Retina is located in the back of the eye. It contains nerves called Rods and Cones. The nerve cells detect light that enters the eye.
  • Optic Nerve – This nerve is the highway to the brain. The brain interprets what the Retina has gathered so that a person can see.

Problems of the Eye

  • Astigmatism – This eye disease can cause objects to be blurry. The objects may blur both close and far away. It is caused by a distorted, oblong shape of the cornea, the film over the eye that is supposed to keep things in focus.
  • Myopia (Nearsightedness) – When people are Nearsighted, they can usually only see things clearly when they are close. Far away things become blurry, and the person will squint to see them. It is caused when the eyeball is longer than usual, or steep, and the light comes into focus not on the retina, but right before it.
  • Hyperopia (Farsightedness) – Just the opposite of Myopia, people with Hyperopia can see things far away just fine. Instead, they have trouble focusing on things close to them, like a computer or a book. This can cause headaches and eyestrain. It is also caused by a distortion of the eyeball, but the light concentrates and comes into focus behind the retina.
  • Blindness – There are many different levels of Blindness. People are completely, totally Blind will see no light at all when their eyes are open. Their brain registers nothing that comes into the eye. Many times, however, blindness is used to describe someone who has a very hard time seeing or focusing. Many times these people can detect shapes, or at least know light from dark. Some people who are “Legally Blind” can actually see figures and objects, but they are so out of focus that they have difficulty recognizing them.
  • Cataracts – Cataracts are most common in people over the age of 55. As the person ages, the lens of the eye loses some of its ability to present clear, sharp images. The result is that objects look cloudy. Cataracts can be corrected with surgery when the problem becomes more severe.
  • Color Blindness – People who are Colorblind cannot distinguish between certain colors. This happens when the cones of the nerve cells are missing pigment. The most common type color blindness cannot tell the difference between red and green. If more than one pigment is missing, the person will also not be able to see yellows and blues. This problem is hereditary and usually only occurs in men.
  • Conjunctivitis (Pinkeye) – This eye problem is caused by inflammation of the membrane that goes right under the eyelid. Someone with Conjunctivitis will have dry, irritated eyes; they may feel gritty. This is also known as pink eye and can be contagious. It is easily treatable with eye drop medication that must be used for a period of time.
  • Dacryostenosis – Dacryostenosis is a medical term for a blocked tear duct. This can occur sometimes from birth and sometimes from an injury to the eye. Sometimes this condition can cause some tearing, so usually it is best to have it surgically corrected if the situation occurs for too long.
  • Injuries – There are many different kinds of injuries that can occur with the eye. The most common is a corneal abrasion, or scratched eye, usually caused by a foreign object in the eye that is rubbed into the eye. People may also have things that puncture or penetrate the eyeball. This can be very serious and the victim should seek the advice of a physician as soon as possible. Chemical burns are also a risk to the eye, so people should be very careful when working with acid or other caustic products. Anyone who gets a chemical in the eye should rinse the eye immediately with water then call a physician.
  • Glaucoma – This disease can begin with increased pressure in the eye. It can be caused over time or in an acute instance. The urgency results in damage to the optic nerve that carries information to the brain. If glaucoma is not treated, the patient may have decreased vision or blindness.
  • Macular Degeneration – Some of the nerves in the central nerves in the retina are called Macula. The degeneration of these nerves can cause vision to become gray and fade. Some people, who suffer from Macular Degeneration, may go blind. There are ways to avoid the degeneration that occurs with age. These include wearing sunglasses, not smoking, and maintaining a normal blood pressure.
  • Retinoblastoma – This is a cancer that occurs in the retina of the eye. This is usually discovered by the time a child is five years old and is very treatable. The most common sign of Retinoblastoma is irregularity of the pupil during an eye examination by a doctor.
  • Retinopathy of prematurity– This is a blood vessel in the retina that should not be there. It occurs in premature babies because the eye development has not had a chance to finish. It can cause vision loss in more severe cases, but better neonatal care has lessened the frequency of this disease.
  • Strabismus – This is the condition that most people refer to as cross-eyed. Either one eye or both may turn in or out, up or down. This can cause double vision sometimes, but usually can be cured with therapy by the eye doctor, sometimes by patching the affected eye.
  • Sty – A Sty is an infection of the eyelid caused by bacteria that are normally present in the eye. When a sty develops, it is usually because the germs get stuck in a hair follicle, such as an eyelash, or a tear duct. Most sties go away by themselves, but eye drops can help the process if it lingers longer.

Eye Glasses

Now that we have learned some of the conditions of the eye and how sight is affected, it is easier to understand what glasses can do for a person. If a person is nearsighted, we learned that it is because the lens of the eye is not doing the job of getting the light to the retina. If a person is far-sighted, then the light is getting past the retina. Either way, the person is not going to be able to see clearly. Glasses are lenses that can aid the lens of the eye get the light back within in the retina so that the nerves can get information to the brain.

The lens of the glasses is measured by using the phrase diopters. People who are nearsighted have negative diopter glasses; people who are farsighted have positive diopter ranges. Some glasses are made from glass, and others are made of polycarbonate plastic. There are many different frames to choose from, and one can also choose glasses that change tint in the sun or come scratch-resistant. Glasses can be very fashionable now, and many people wear them. As people age, they become increasingly farsighted and will sometimes purchase “reading glasses” from a store to correct the mild vision impairment.

Eye Safety

As we have learned, the eyes are very important, and also very delicate. It is important to take precautions to avoid injuries to the eyes. Even though over a million eye injuries occur every year, most of them could have been avoided if the person were practicing good eye safety measures. Some of these precautions may seem pretty simple, but people often ignore them. Keep sharp objects away from the eye, and never run with sharp things in hand. Turn spray nozzles away from the face to avoid chemicals getting into the eye, and wash your hands after using chemicals. Wear protective eye safety glasses when using power equipment and participating in sports that could be dangerous to the eye. Never look directly at the sun for a long time, because this could cause burning of the eyes. Stay away from fireworks. If a foreign object gets into the eye do not rub your eyes, gently rinse with water. If it cannot be gotten out, see a doctor.

Another way to care for the eyes is taking measures to protect vision while aging. If any eye infection develops, see a doctor so that it can be corrected early enough that it does not cause permanent damage. This includes pink eye, a clogged tear duct, and any other condition that seems to be affecting the vision. Eating foods that contain vitamins to support eye heath can also aid in long term vision. Vitamin A is the most recognized vitamin known for eye health. It is found in carrots, kale, and spinach. Selenium helps prevent cataracts, and this can be found in sunflower seeds and garlic. Omega-3 fatty acids, found in salmon, are known to be good for overall eye health as well. Other good things to eat are broccoli, avocados, eggs, and tomatoes. Taking good care of your eyes throughout your life can decrease the probability that vision will fade with age.

Learn More!

The following sites are all about the eye and are designed for kids like you. Learn more about the anatomy of the eye, diseases that can affect the eye, and about glasses and eye safety. You can explore wavelengths of light. There are games! Can you find the site that play tricks on the brain with optical illusions? Explore these sites with, what else? Your eyes!

  • Kid's Health: Your Eyes: This site is all about how the eye and how the different parts of the eye work. By investigating the eyes of a friend, it’s possible to look at many parts of the eye.
  • Teen's Health: Eyes: This article shows the many things our eyes can reveal like space and size, and the many parts of the body that work together to protect this delicate organ.
  • Kid's Health: Glasses and Contact Lenses: Learn why some people need glasses and others don’t. Several eye complications are discussed.
  • See All You Can See: Parts of the Eye: Flash games and diagrams from the National Eye Institute and National Institute of Health show the parts of the eyes and ways to protect your eyes when playing sports or participating in other activities.
  • Neuroscience For Kids - The Eye: The eye uses wavelengths of light to view the things around us. This article describes the parts of the eye and how they work to do that.
  • Eyes - how your eyes work: Learn how the eye works like a camera and how each part of the eye corresponds to a part of the camera.
  • The Children's University of Manchester: The Brain and Senses: Discover how the brain contributes to the work of the eye with a fun flash diagram. Includes a self-test for fun.
  • Neuroscience for Kids - Fill In: This blank diagram allows readers to test their knowledge of the parts of the eye.
  • KScience: This interactive quiz of the parts of the eye will let the user know right away if they are right or wrong. Test your skills!
  • Eye Can Learn: These fun exercises measure how well the eye is working in different areas such as perception, tracking, focusing, and “eye teaming.”
  • Optical Research Associates | Optics For Kids Home: Optics is all about physics, and optics is all about the eye. Learn how light plays into the way the eye works.
  • Optical Society of America: Exploring the Science of Light: This site will guide the reader through activities and information on many optic categories such as acousto -optics and retro reflection using tools such as Jell-O and laser pointers.
  • Molecular Expressions Microscopy Primer: Physics of Light and Color: Explains light and how it reacts with the eye to give us sight. Different parts of light are discussed such as wavelength, fluorescence, speed, reflection, and refraction.
  • Eye Movement: Mike from Monsters, Inc. introduces eye movement and how our eyes react to movement around us. The reader can click through screens at the bottom of the page. A self-quiz can check how much the reader remembers.
  • A Kids Eye Safety Guide: Our eyes are one of the most important organs of the body, and it is important to keep them protected. This quiz should be taken with the parent, and it shows ways that kids should be safer with their eyes.
  • History Detectives Kids: This site from PBS will have you test your “spying” talents by trying to figure out the object that is shown. Careful! Your eyes can deceive you!
  • PBS: Cyber chase: Use the power of sight as a guide leads the player through a maze and puzzle.
  • Learning Activities: Hand-eye coordination is not something that necessarily comes naturally for some kids. Try these games and activities to increase abilities!
  • NIEHS Kids Page -- Optical Illusions: Sometimes the brain can play tricks with the eyes. This page of optical illusions fascinates, as the watcher cannot believe their eyes!

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