Contact lenses sit directly on your cornea. They're made from different materials and can be hard or soft, reusable or disposable. They have plenty of advantages—no glare from glasses, and no worrying about losing or breaking your specs. But they have their risks. In fact, one in 20 users have complications.
Corneal abrasions are a constant risk, not only from placement of the lens, but from the lens rubbing on the cornea with each blink. Conjunctivitis, as well as allergies to either the lenses or the cleaning solutions, are common and are related to the type of lens and whether you wear them overnight. Bacteria can invade your eyes if they're irritated by contacts, causing severe corneal infections that can endanger your vision.
Disposable lenses do not reduce the chance of infection, as the lens cleaning solution may be the source of bacteria. You should write the date on the bottle when you open a lens wetting or cleaning solution and throw it out after a month.
Lenses can rob your cornea of oxygen, causing your body to grow blood vessels into the normally clear cornea, impairing your vision. So, make sure you take them out every night unless they're specifically marked as continuous wear. Follow the manufacturer's guidelines carefully to avoid corneal damage.
Find out more about this book:You: Being Beautiful - The Owner's Manual to Inner and Outer Beauty