A contact lens is a medical device that rests on the sclera (the white part) of your eye. They are designed to correct your vision, enhance your eye color or treat certain eye diseases.

Each lens surface is either convex or concave; it can also be spherical, aspheric, cylindrical or flat (plano). This shape causes light rays to converge or diverge.

They correct your vision

When contact lenses are properly worn and cared for, they provide clear, comfortable vision. Although new wearers may experience some blurriness while their eyes adjust to the lenses, these symptoms will usually dissipate shortly.

Your eye doctor will measure the shape of your cornea and pupil during a dilated eye exam, then give you a prescription for contact lenses with a precise refractive power to correct your vision problems. Your prescription will also include specific instructions for proper lens wearing and storage.

Most contact lenses are made of soft, water-absorbing plastic, and they can be purchased in disposable format to be used daily and thrown away, or in non-disposable form that is kept in a disinfection solution for up to a month. Depending on your eye doctor’s recommendation, you can purchase contact lenses that correct both nearsightedness and age-related farsightedness (presbyopia), called multifocal contact lenses. To use these lenses, first wash your hands and then tip the lens from its storage case into your cupped hand.

They’re easy to wear

Putting in and taking out contact lenses requires only a little practice. Most people who wear them for the first time are apprehensive because it involves touching their eyeball, but it really isn’t that scary once you learn how to do it properly.

You should always wash your hands before handling your lenses. Rinse and rub them with contact solution before you put them in or take them out, and be sure to use a commercially prepared sterile solution for cleaning and storage. Homemade saline solutions are not sterilized and can contain traces of minerals and chemicals that can cause eye infections or damage your lenses.

Decorative contacts are available without a prescription at some retailers, but they can pose serious health risks if they’re not correctly fitted and cared for. Ask your optometrist for recommendations and for an eye exam to ensure you have the best vision possible with safe, healthy decorative lenses. They can also help you find a lens that is beginner-friendly.

They’re convenient

For many people, contact lenses offer a greater level of convenience than glasses. They can be worn with non-prescription sunglasses and other decorative eyewear, and they don’t cover makeup or piercings like traditional glasses can.

Contact lenses are also less likely to fall off during sports or other physical activities, and they don’t fog up in cold weather or break like traditional spectacles. Additionally, they’re comfortable to wear and allow a wider field of view than most eyeglasses do.

Rigid contacts are typically more uncomfortable than soft contact lenses at first, but they become more comfortable with time and some practice. For those with astigmatism, there are a variety of soft and gas permeable lenses available that correct both up-close and faraway vision at the same time.

Some contact lenses are disposable and discarded after a single day of use (called daily disposables) while others can be worn for up to a month with regular cleaning and disinfecting solutions. There are also other, more specialized types of contact lenses that can correct specific problems and treat conditions like glaucoma.

They’re safe

All contact lenses that are approved by the FDA have been studied and determined to be safe when specific care and wear procedures are followed. Serious eye infections that can lead to blindness affect up to one out of 500 contact lens wearers per year and these problems are usually easily prevented when proper care practices are followed.

A contact lens worn too long, improperly cleaned or stored and sleeping while wearing contacts can all cause bacteria to build up on the surface of the cornea and these bacteria can cause serious eye infections like keratitis, conjunctivitis, or corneal ulcers. Symptoms of infection include blurry vision, red and irritated eyes, or white spots visible in the colored part of the contact lens.

Don’t buy contact lenses from over-the-counter retailers or novelty stores because these products may have been contaminated with water and micro-organisms that can cause serious eye infections. Make sure that you have a valid and current prescription for your lenses before buying them and report any online sellers that sell these devices without a prescription to the FDA’s consumer complaint program.