Have you ever put on a blindfold and pretended that you couldn't see? You probably bumped into things and got confused about which way you were going. But if you had to, you could get adjusted and learn to live without your sight.

Lots of people have done just that. They have found ways to learn, play, and work, even though they have trouble seeing or can't see at all.

How Seeing Happens

Your eyes and your brain work together to see. The eye is made up of many different parts, including the cornea, iris, lens, and retina. These parts all work together to focus on light and images. Your eyes then use special nerves to send what you see to your brain, so your brain can process and recognize what you're seeing. In eyes that work correctly, this process happens almost instantly.

When this doesn't work the way it should, a person may be visually impaired, or blind. The problem may affect one eye or both eyes.

When you think of being blind, you might imagine total darkness. But most people who are blind can still see a little light or shadows. They just can't see things clearly. People who have some sight, but still need a lot of help, are sometimes called "legally blind."

What Causes Blindness?

Vision problems can develop before a baby is born. Sometimes, parts of the eyes don't form the way they should. A kid's eyes might look fine, but the brain has trouble processing the information they send. The optic nerve sends pictures to the brain, so if the nerve doesn't form correctly, the baby's brain won't receive the messages needed for sight.

Blindness can be genetic (or inherited), which means that this problem gets passed down to a kid from parents through genes.

Blindness also can be caused by an accident, if something hurts the eye. That's why it's so important to protect your eyes when you play certain sports, such as hockey.

Some illnesses, such as diabetes, can damage a person's vision over time. Other eye diseases, such as cataracts (say: KAH-tuh-rakts), can cause vision problems or blindness, but they usually affect older people.

What Does the Doctor Do?

A kid who has serious trouble with vision might see an ophthalmologist (say: af-thal-MAH-luh-jist), a doctor who specializes in eye problems. Even babies might see an ophthalmologist if their parents think they might be having trouble seeing.

At the doctor visit, the doctor will talk with the parents and the kid (if the kid is old enough to describe what's going on). A doctor might use an eye chart to find out how well the kid can see. You've probably seen these charts that contain letters of different sizes. It's a way of testing how well a person can see. Someone with really good vision would be able to read certain letters from 20 feet (6 meters) away.

Eyesight this good is called 20/20 vision, although some people can see even better than that. The numbers change depending on how clearly a person can see. The larger or closer something needs to be in order for it to be seen, the worse a person's vision is.

Many times, glasses or contact lenses are all that's needed to help kids see better. But if glasses and contact lenses can't make someone's vision any better — and the person needs to get really close to something to see it — he or she may be considered blind. For instance, someone with good vision might be able to see an object from 200 feet (61 meters) away, but someone is considered blind if he or she needs to be 20 feet (6 meters) away to see the same object.

Babies and little kids won't be able to use the eye chart, but doctors can check their vision by doing special vision tests or something as simple as putting a toy in front of the child to see if he or she can focus on it.

The ophthalmologist also will examine the kid's eyes using special medication and lighting that allows him or her to see into the eyeballs. The ophthalmologist will look at each part of the eye to check for problems, such as a cataract (cloudiness of the eye's lens). Once the doctor knows what's causing the vision problem, he or she can begin planning how to treat it.

In some cases, an operation can help improve a kid's vision. For example, if a kid has a cataract, doctors may do surgery to remove it.

Is Learning Different?

A baby who is blind can still learn and develop normally. But the baby's parents will need the help of specialists who know how to help blind children. It's often a great idea for the child to attend special learning programs designed just for little kids who have trouble seeing. These programs would make the most of the senses that the kid does have, such as touch, hearing, smell, and taste.

Touch comes in handy when a child is older and wants to read books. Kids who are visually impaired can learn to read by using a special system called braille. Braille is a way of expressing letters, words, and thoughts. To read braille, a person feels a series of little bumps that are associated with letters in the alphabet. For instance, "A" is represented as one bump. Computer programs and other devices that can "see" turn the words on a page into braille.

Hearing is another important sense if a kid has vision problems. Some devices can read out loud what's written on a page. With special equipment, a visually impaired kid can read almost anything. These kinds of technologies can be helpful in learning. Kids who are blind might attend a special school, or they might attend regular classes, aided by special devices and specialists.

Hot Dog!

Kids who have vision problems will get help from their parents, doctors, and teachers. When they are older, some of them may get a hand — or should we say a paw? — from a guide dog. These helper dogs are trained to be a blind person's eyes. That means the dog learns to be very alert to surroundings so he or she can be a good guide for the person.

Not only are these dogs great friends, they give blind people independence, so they can accomplish what they want to accomplish.

Many blind people have gone on to do amazing things in many different fields, including music, the arts, and even sports. Serious vision problems didn't stop runner Marla Runyan. She was the first legally blind person to ever qualify for the Olympics!