If you want to wear contact lenses, you must first see an ophthalmologist, or in some states, an optician. This is the case even if you don't wear glasses, and want contacts to change your eye color.

Contact lenses are medical devices that need to be properly fitted by an eye-care specialist. This is why in the United States contacts can be legally purchased only with a valid written prescription.

In addition, your prescription could note how often your contact lenses must be replaced, which could be once a month, every two weeks, once a week, daily, etc. Often the lens brand includes this information, but the real judge is your eye care practitioner, who knows which replacement option is best for your eyes and lifestyle.

Many doctors highly advocate both disposable and frequent alternating contact lenses: they are an excellent choice health-wise, as there is less opportunity for protein and bacteria to build up on them.

Contact lenses are made of different types of plastic, but they are divided into two main groups: soft, or rigid gas-permeable, also commonly known as GP lenses. Rigid gas-permeable contact lenses take longer to adapt to, but are sturdy and resistant to deposit buildup. The replacement program of a contact lens refers to how long you can wear them before you need to dispose of them. With GP lenses, you generally replace them every couple of years, because they are made of durable material.

The selection of contact lenses available can best be described as gigantic. Don't worry about becoming besieged, though: contact lenses can be broken down into several main categories based on what they're made of, how often you need to replace them and whether you can sleep in them. So look for the category that suits your requirements.