According to the Prevent Blindness organization, about 46 million Americans wear contact lenses, a technology first conceptualized by Leonardo da Vinci in 1508.

While most of us learned the basic care rules from our optometrists when we first were prescribed our contacts, October is a perfect time for a refresher. In observation of National Contact Lens Safety Month, we’ve put together a quiz to discover if you are seeing clearly or if things are a bit blurry when it comes to caring for your contact lenses.

True or false: If I don’t have my contact solution with me, water will work.

This is false. You should only use the contact lens solution your eye care provider recommended, which is specific to you and your brand of contacts. Never use water, homemade saline, someone else’s solution, old or expired solution, or saliva (yuck!) to clean your contacts. Keep an extra bottle of your recommended solution in your purse or in your desk at work so you aren’t tempted to DIY a lens cleaner.

True or false: It’s fine to wear makeup with contact lenses.

This is true, but with some caveats. Optometrists recommend that if you have soft contact lenses, you put them in before doing your makeup; but if you have rigid gas permeable lenses, you should put them in after applying cosmetics. Also avoid lash-extending mascara, as the fibers can irritate your eyes, and waterproof mascara, as it may stain soft contact lenses. You should keep things like nail polish and remover, eyelash, perfume and cologne away from your lenses; the chemicals in these can damage the plastic of the lenses. Finally, remember to remove your contacts before you wash off your makeup.

True or false: I should use the same contact lens case until I get a new prescription.

This is false. Your contact lens case can turn into a breeding ground for bacteria, which could lead to discomfort and infection. You should replace your case every six months or when you start a new bottle of solution. You should also clean, rinse and air dry your case daily.

True or false: I should never share contacts with someone, even if we use the same brand.

This is true. Contact lenses are just like any prescription: it is something a healthcare provider has prescribed specifically for you and only you. There are multiple factors that a licensed eye care professional considers when writing a contact lens prescription: your vision, the curve of your cornea, the diameter of the area where your contact will sit and more. Not only can sharing contacts with someone else lead to infection, it could also damage their eye.

For more tips on contact lenses and vision safety, visit the websites for the American Optometric Association and Prevent Blindness. And if it’s been more than 12 months since your last contact lens exam, visit click on the “find a physician” button at the top of this page to search for ophthalmologists near you.