ORLANDO, Fla. -

Many of us think that cataracts only affect the elderly. But doctors say that's quickly becoming a medical myth.

New numbers show that more Americans are being diagnosed with the eye disease. And a lot of those patients are younger than you might expect -- some, even in their teens.

The eye disease is the leading cause of blindness in America -- and doctors say that making important lifestyle changes now, no matter what your age is, can protect your vision down the road.

Take William Newland, whose career as a pilot depends on his eyesight.

"I can't fly an airplane unless I can see perfectly," says Newland.

But at age 51, his vision became blurry.

"Like looking through a dirty glass," says Newland.

He's one of the many middle-aged patients who are diagnosed with cataracts -- a common condition in seniors.

According to the consumer health group, Prevent Blindness America, nearly 25 million Americans have cataracts, up 19 percent since the year 2000.

The disease is basically a loss of clarity in the lens of your eye. It makes your vision blurry, hazy, or distorted.

"We say that if you live long enough, you will develop a cataract," says Dr. Konrad Filutowski, an ophthalmologist in Orlando.

He says that he sees patients of all ages with cataracts -- even those in their teens.

"I have done just recently somebody's surgery who was 18 years old. The boy is 18 years old," says Dr. Filutowksi.

That probably sounds unbelievable to a lot you -- but listen to this...

Dr. Filutowski says things like diabetes, medication like steroids, smoking, and sun exposure can all raise your risk of cataracts if you're younger than 65.

That's why it might be a good idea to quit smoking, watch your weight and protect your eyes from sunlight.

"Always protect your eyes from strong sunlight," says Dr. Filutowski. "Good quality, high quality sunglasses that are more of the wraparound, that are comfortable, that you're going to be wearing when you go outside."

No matter your age, remember that cataracts are almost always treatable with surgery. Your cloudy lens is removed and replaced with a clear, artificial one.

"Even if you're very young, it can be a cataract, and there's a great solution to cataract in any age group, which is cataract surgery, which is very successful with excellent track record."

Since getting that surgery, William Newland says he's had perfect vision.

"It really reassured me that I was going to be able to continue in my career," says Newland.

Cataract surgery is performed more than any other surgery in America. And it's usually covered by most health insurance plans, including Medicare.