In the 1997 movie "Contact," astronomer Ellie Arroway (Jodi Foster) gets a message from outer space instructing her to build a machine.

Will it destroy the earth, or redefine space travel? She and Palmer Joss (Matthew McConaughey) wonder what the real deal is.

When it comes to your own contacts — lenses, that is — you, too, may wonder what's up.

Are they safe? Are you using them correctly?

The Centers for Disease Control and Prevention has just issued a warning about the risk for eye infections that should set the record straight.

They say if you abide by the instructions that come with the lenses and from your eye doctor, all's well. But if you don't, you could end up in big trouble.

And 99 percent of the 40 million contact lens wearers in the U.S. admit to having lousy contact-lens hygiene in some way: They wear contacts longer than prescribed, reuse saline, and use tap water for storage.

Contacts rest on your cornea, making it vulnerable to bacteria on your lenses.

Almost 20 percent of eye infections reported to a federal database led to lasting damage, such as scarring of the cornea and even vision loss. So, the CDC recommends:

• Don't sleep in contacts; that boosts infection risk by six to eight times. Even lenses with "high oxygen transmissibility" can deprive the cornea of oxygen, triggering corneal swelling.

• Replace contacts as recommended.

• Follow hygiene recommendations every time you put contacts in or take them out.