If you use contact lenses, be warned: a new report finds that you may be damaging your eyes greatly and not even realize it. The report from the CDC finds that misusing contact lenses thinking it’s no big deal is a mistake, and can result in some serious eye damage.

The Food and Drug Administration received 1,075 reports of contact lens related corneal infections between 2005 and 2015, and about 20 percent of those reports involved some serioius eye damage — and about a quarter of those cases could have been avoided entirely, had contact lens users just been careful, according to a CDC statement.

“Contact lenses are a safe and effective form of vision correction when worn and cared for as recommended,” said Michael Beach, Ph.D., director of CDC’s Healthy Water Program. “However, improper wear and care of contact lenses can cause eye infections that sometimes lead to serious, long-term damage.”

Contact lenses are perfectly safe for your eyes — what’s not safe is when you use them against safety guidelines. Wearing them for an extended non-approved period is the most common violation at 11 percent, and then using lenses beyond the prescription at 8 percent. Wearing them overnight occasionally accounted for 7 percent of incorrect users, and others stored the lenses in water or wore them while swimming.

This can open up your risk of infection, which was the case about 13 percent of the time.

“Around 41 million people in the United States wear contact lenses and benefit from the improved vision and comfort they provide,” said Jennifer Cope, M.D., M.P.H., medical epidemiologist in CDC’s Waterborne Disease Prevention Branch. “While people who get serious eye infections represent a small percentage of those who wear contacts, they serve as a reminder for all contact lens wearers to take simple steps to prevent infections.”