Contact lens users may want to take a closer look at the rules for wearing their lenses safely. More than 30 million Americans wear contact lenses to improve their vision.

According to a new study, a lot of them may be in danger of eye problems.

Contact lens wearers answered a questionnaire that tested their basic knowledge about contacts. Most could name at least one eye complication that contacts can cause, which is irritation and redness. And 85% thought that they were following the rules for wearing them and keeping them clean.

But fewer than 1% were actually following all the recommendations. The American Optometric Association offers these tips for properly wearing contacts:

• Wash and dry your hands before you touch your contacts
• Clean your contacts regularly
• Store your contacts in their proper case
• Clean your case after each use
• Replace your contacts case at least every three months
• Only use fresh solutions for cleaning and storing your contacts
• Avoid using tap water for cleaning or storing your lenses
• Keep your lenses out of your mouth
• Replace your lenses according to the schedule your eye doctor provides.

Talk to your eye doctor for a full rundown of instructions on caring for your own contact lenses.