If you wear contact lenses, you’re in good company. Roughly one in seven teens and one in six adults in the U.S. wear contacts — nearly 45 million people. And you’re likely doing it wrong. A study by the Centers for Disease Control and Prevention found six of seven lens wearers reported at least one behavior putting them at risk for a serious eye infection.

The most common mistakes were not swapping out contacts or lens cases often enough, sleeping while wearing the lenses or wearing them while swimming. These and other bad practices can have serious consequences, including blindness.

The CDC used on online survey of nearly 5,000 adults and more than sixteen-hundred teens to ask about contact lens use. Among the findings? Young adults, by a significant percentage, were more likely that youngsters or older adults to report a risky behavior. The researchers cited a number of possible reasons, including that teens living at home have adults around to reinforce good lens hygiene. Also, young adults often have less money, live in crowded spaces such as dorms with shared bathrooms, and have more impulsive lifestyles.

Lax lens care can have serious results. Infrequent lens and storage case replacement can lead to microbial infection. Swimming or showering can transfer microorganisms to the lens and then the eye. And while some lenses are approved for overnight wear, sleeping with lenses invites eye infections.

The authors say those who want to change habits in young adults can use strategies such as appeals to vanity. The goal is that good behavior as adolescents and young adults will carry through in later years to help protect the gift of eyesight for a lifetime.