Contact lenses are miraculous pieces of plastic that allow you to see without glasses. In most cases, contact lenses are used as a substitute for glasses, allowing you to dispense with them. Contact lenses may also be used to treat certain eye diseases or may be used for cosmetic purposes to change the apparent color of your eyes.

Successful contact-lens wear requires a "partnership" between the fitter, that is, an ophthalmologist, an optometrist, or possibly an optician, and you, the wearer.

The fitter must first decide if your eyes are healthy enough to wear contact lenses. If so, the fitter then fits the correct lenses for your eyes and your needs and teaches you how to use and care for them.

The fitter should be available if problems develop; if not available, the fitter must then have system in place to address those situations.

You must follow the instructions, care for, and wear the lenses correctly, and return as required for routine and emergency care.

A fitter can be an ophthalmologist, an optometrist, or possibly an optician.

Ophthalmologists are doctors who have graduated from college, and a school of medicine (MD) or osteopathy (DO), after which three to five years of additional training are required and spent studying about eye examinations (including fitting of contact lenses and glasses), diagnosis and treatment of eye diseases, and performing eye surgery. Ophthalmologists perform both conventional surgery and laser surgery.

Optometrists have graduated from a school of optometry (OD), where they are trained in eye examinations, fitting of contact lenses and glasses, and depending on state licensure, treatment of certain eye diseases. Optometrists do not perform conventional eye surgery or laser surgery.

Opticians fit glasses based on the prescription of an ophthalmologist or an optometrist. In some states, opticians may fit contact lenses. Opticians do not perform eye examinations, do not diagnose or treat eye diseases, and do not perform surgery.

Soft lenses and rigid gas permeable (RGP) lenses are the main lenses available. Each has specific indications as well as a specific wear and care regimen. The older hard (PMMA) lenses are rarely used today and have risks similar to RGP lenses. There are larger scleral lenses available for special eye conditions.

Contact lenses are mainly used to avoid having to wear glasses in conditions such as nearsightedness, farsightedness, and astigmatism or to avoid the use of bifocals (multifocal lenses).

They may also be used to treat other conditions. Keratoconus is a condition in which the surface of the eye has a very irregular shape (astigmatism). When glasses no longer provide adequate vision, contact lenses are used.

Contact lenses are often used after refractive surgery when under- or over-corrections occur. After surgery, and in some cases of eye diseases of the cornea, bandage soft contact lenses may be used to allow the cornea to heal or may be used to alleviate pain.

Some lenses are meant for daily wear. With daily wear soft lenses, you wear the lenses for one day and then discard them. This allows one to dispense with solutions, cleaning, and disinfection of the lenses. It allows intermittent wear such as weekend or occasional wear, as desired.

Most soft lenses and some RGP lenses are worn for a day and then removed, cleaned, and disinfected each night. Soft lenses are usually replaced on a regular basis, which varies from one week to one month to three months to one year. RGP lenses may last for years with regular care.

Extended wear lenses, usually soft, are worn overnight for one week and then replaced every one to two weeks. Trying to extend the wear of lenses beyond the recommended replacement schedule is a false economy and an invitation to potential disaster.

Overnight wear decreases the amount of oxygen available to the eye and increases the (rare) chance of infection by fourfold. Because of this, some practitioners do not recommend extended wear of contact lenses. Newer lenses may be safer.

Problems resulting from contact lens wear range from the inability to remove the lenses (usually after first being fit) to blindness from infections. Proper fitting, instruction, and care and maintenance can prevent most problems.

When being fit with contact lenses, the fitter should provide the patient with information as to what to do in case of a problem (call the office, go to the emergency room, etc.).

After being fit, inability to remove lenses occasionally occurs. Call your fitter for instructions as to how to proceed.

The most common reasons for contact-lens wearers to seek care is irritation of the eyes, redness, or blurred vision. These can be caused by the lenses wearing out or warping, a change in the eyes requiring new lenses, poor fitting of the lenses, poor care of the lenses, or sensitivity to solutions. These relatively minor inconveniences must be evaluated because they may signal the onset of corneal ulcers and deeper infection.

With the glut of contact-lens solutions available, it is important to use only the solution recommended by the fitter. Some solutions may be incompatible with certain lenses or may contain components, such as Thimerosal (20% of people are allergic to this substance), which are not compatible with the eyes of certain people.

One major concern, from the wearer's viewpoint, is the danger when a contact lens slips off the eye. The lens sits on the surface of the eye but cannot travel "back to the brain" because the clear covering of the eye goes under the eyelid and keeps the lens from going further back.

If the lens cannot be repositioned on the cornea, it is under the eyelid and can be easily slid or moved to its correct position on the cornea (sometimes requiring the help of the fitter). It will do no harm if it is under the eyelid for a number of hours.

Redness of the eyes associated with pain, blurred vision, and light sensitivity is more serious and may signal a potentially blinding condition, such as a corneal ulcer due to an infection.

Abrasions (scratches) on the surface of the cornea (corneal abrasions) usually result from insufficient oxygen reaching the surface of the eye, although they may also result from dirt or other foreign bodies getting under the lens. It may be due to either over-wear of the contact lenses or lenses that are not tolerated by the eye. These disturbances of the cornea not only may be very painful but also may predispose the eye to a serious, blinding infection.

Occasionally, someone inadvertently soaks his or her lenses in cleaning solution or soap solution, resulting in redness of the eye with a great deal of pain. This is extremely uncomfortable but usually causes no permanent damage. Drops and irrigation of the eye may be necessary to relieve the pain.

Makeup may get under a lens and cause irritation or a greasy film on the lens, making it difficult to see clearly. Sometimes polishing in the office will be necessary to remove this film.

It is important to keep in mind that any of these eye complaints may occur and have nothing to do with the contact lenses and may be signs of other unrelated eye conditions such as infections, cataracts, or glaucoma. It may be necessary to see your eye-care professional for the correct diagnosis and treatment.

Any change in the condition of the eyes of contact-lens wearers must be evaluated for the cause and possible treatment. Whether or not these eye complaints are due to the contact lenses, they still must be diagnosed and treated. When in doubt, call your fitter for information as to how to proceed; remember that opticians do not treat eye diseases.