Contact Lenses

What are contact lenses?

Contact lenses are small, curved pieces of plastic shaped to fit your eyes to correct some vision problems, such as nearsightedness or farsightedness. Contact lenses float on the tear film in front of the cornea (the clear outer layer on the front of the eyeball). Contact lenses help your eyes focus the same way as glasses.

Contact lenses can correct most of the vision problems that glasses correct. They can also correct some problems that glasses cannot.

When are they used?

Often, people wear contact lenses because they do not like how they look with glasses. Contact lenses may be more practical than eyeglasses if you participate in sports or work at jobs where glasses could get in the way. Also, contacts give better peripheral (side) vision than glasses do.

People may prefer contact lenses over glasses if they are very nearsighted or have had cataracts removed. For them, glasses can produce uneven vision. Contact lenses may also provide better vision for people with corneas damaged by disease or injury.

What are the main types of contact lenses?

The two main types of contacts used today are soft contact lenses and gas permeable (sometimes called rigid or hard) contact lenses.

• Soft contact lenses are made of hydrophilic (water-loving) plastics. They absorb liquids and are kept moist so that they stay soft and mold easily to the cornea. For many people, they are the most comfortable type of contacts.
• Gas permeable lenses are made of durable, slightly flexible plastic that allows oxygen to reach the cornea. They are easier to care for than soft contact lenses. Gas permeable lenses have replaced the original hard lenses that were made of polymethylmethacrylate or PMMA. The original hard lenses were durable and provided good vision, but they did not allow much oxygen to reach the cornea. Lack of oxygen can damage the eyeball.

Both gas permeable and soft contact lenses can be made into bifocals. Also, both types can be tinted either for use as sunglasses or for cosmetic reasons.

How can I get contact lenses?

You need a thorough eye exam by an ophthalmologist (a medical doctor who specializes in eyes) or an optometrist, who will:

• determine whether your eyes are suitable for contact lenses
• recommend either gas permeable or soft lenses
• check your eyes regularly after you begin wearing your lenses full time.

When you first start wearing contacts, you may feel a slight discomfort when they are in your eyes. This is normal. If you have any pain in your eyes that does not go away after removing your contacts or that returns each time you wear your contacts, see your eye doctor. Checkups of your eyes and lenses are recommended 1 week, 2 weeks, 1 month, 6 months, and 1 year after you first get them.

What precautions should I take with contact lenses?

• When you first start wearing contacts, carefully follow the break-in schedule prescribed by your eye doctor.
• Wash your hands with soap and water before you put in or take out your contacts.
• Do not wear your contacts while swimming. Soft lenses absorb chemicals from the water. Gas permeable lenses will float out of your eyes.
• Contacts should not be worn while you are sleeping. Sleeping with your lenses in your eyes may damage your eyes by keeping the cornea from getting enough oxygen. Also, it places you at risk for infection. For extended-wear lenses, follow your eye doctor's recommendations for the length of time you can safely leave the lenses in your eyes.
• Always put your contacts in your eyes before you put makeup on. Use water-soluble makeup. Do not use lash-building mascara, because particles may get into your eyes. If you put eyeliner between your lashes and your eyes, you may discolor soft lenses permanently.
• Do not put contact lenses in your mouth to moisten or clean them. It may increase your risk of eye infection.
• See your eye doctor promptly if you have burning, redness, pain, unusual light sensitivity, or blurred vision.

What are some problems with contact lenses?

You may find it difficult to wear contact lenses if you have:

• very irritated eyes from allergies or exposure to dust or chemicals at your job.
• an overactive thyroid gland, uncontrolled diabetes, or severe arthritis in your hands.
• dry eyes because of pregnancy, birth control pills, diuretics, antihistamines, or decongestants.
• an eye disease that affects the health of the surface of the eye.

Possible problems include:

• eye infections
• allergic reactions to lens care solutions and particles on or in the lenses
• inflammation (redness) of the eye
• scratched cornea
• a change in the shape of the cornea
• abnormal blood vessels growing into the normally clear cornea.