Contact Lenses

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About contact lenses

Many people wear contact lenses to correct their vision. The reasons for choosing contact lenses over glasses or refractive eye surgery (which corrects the shape of the cornea) include lifestyle, sports and appearance.

Contact lenses are tiny saucer-shaped pieces of plastic. They are placed on the cornea of the eye, and float on a thin layer of tear fluid. In some cases, contact lenses may offer better vision correction when compared to glasses because they provide more natural vision. Contact lenses move with your eye, and will not block what you see.

Types of contact lenses

Several types of contact lenses are available.

Hard lenses are made of a firm polymer plastic material. They are easier to keep clean because they are less likely to absorb foreign material from the eye or environment. You must remove hard lenses before you go to sleep because they restrict the flow of oxygen to the cornea, which needs oxygen to stay healthy.

Soft lenses are less durable, but are more comfortable because they are made of a softer plastic called hydrogel. Because they contain more water, they permit a better flow of oxygen to the cornea. However, the material is also more porous, so there is an increased risk of eye irritation and infection due to contamination from things such as bacteria or dust from the environment. Usually you remove soft contact lenses from your eyes at the end of each day.

Extended-wear lenses are soft contacts that have been licenced for continuous wear for up to 30 days and nights without being removed.

Rigid gas permeable lenses combine the features of hard and soft contacts. They permit the passage of more oxygen to the cornea than hard lenses do. They are more effective for people with astigmatism (when your eye isn't completely round, resulting in blurry or distorted vision, eyestrain and headaches).

Corneal reshaping or refractive lenses are rigid gas permeable contact lenses that are custom fitted by an eye care professional. They are worn overnight, and are intended to reshape the cornea to correct minor degrees of nearsightedness or astigmatism in adults. These lenses do not correct vision while they are worn. Instead, you would have a corrected vision several hours after wear, because your cornea has been temporarily reshaped while you sleep. The procedure is called orthokeratology, and the results are variable. Only an eye care professional with specialized training should fit you for this type of contact lens.

Contact lenses are medical devices that provide benefits while posing certain risks. If you wear contact lenses, you should take steps to minimize these risks and protect your vision.

Potential adverse health effects

The most common eye problems encountered by contact lens users are:

  • itching
  • dryness
  • burning
  • excess tearing
  • sensitivity to light
  • occasional blurred or distorted vision

These problems may be worsened by improper care or cleaning of contact lenses, which may also increase the risk of developing an eye infection.

Clinical studies suggest that the extended use of contact lenses, particularly overnight, increases the risk of developing potentially serious conditions such as:

  • ulcerative keratitis or corneal ulcers. An ulcer can perforate (make a hole in) or scar the cornea in 1 or 2 days, leading to permanent scarring of the cornea or even blindness.
  • limbal stem cell deficiency, a rare condition where stem cells in the border of the cornea and the white of the eye inadequately produce enough new cells to replace the old ones in the cornea. In early stages, it can have no symptoms or nonspecific symptoms such as pain, light sensitivity, decreased vision or tearing. It can progress to corneal scarring, inflammation and blood vessel development, which can lead to loss of vision.

Many eye doctors advise their patients not to use extended-wear contact lenses.

Lifestyle considerations

Smokers are 8 times more likely to develop corneal ulcers than non-smokers, no matter which type of contact lenses they wear.

Anything that causes dry eyes, including birth control pills, alcohol, air travel and allergy drugs like antihistamines can make contact lenses uncomfortable, and can increase the risk of an eye infection. Environmental contaminants, such as dust, smoke, sprays and pollen, can also irritate your eyes when you wear contacts.

Minimizing your risk of adverse health effects

The most important step you can take to minimize your risk of adverse health effects is to have your contact lenses prescribed and fitted by a qualified eye care professional. You should also participate fully in the recommended follow-up care, including regular visits to an eye care professional.

If you experience blurred or hazy vision, or develop a pain in your eye while wearing contact lenses, remove the contact lenses immediately. If the pain or blurred vision does not go away within a few hours, or if it gets worse, contact your eye care professional or go to the nearest emergency department. In such situations, we recommend that an eye care professional evaluate your corneal surface.

Follow these other steps to minimize the risk of adverse health effects:

  • Read all of the patient information pamphlets that come with your contact lenses.
  • Clean and care for your contact lenses as recommended by your eye care professional.
  • Wash your hands thoroughly before handling your contact lenses.
  • Do not use tap water or saliva to clean contact lenses.
  • Do not switch brands of contact lens solutions on your own, as this may lead to irritation or reactions that are more toxic. If the preservative in your contact lens solution becomes irritating, consult your eye care professional.
  • Do not wear your contact lenses for longer than recommended by your eye care professional.
  • Remember that overnight wear of contact lenses, including those labeled as extended-wear contact lenses, is linked to an increased risk of serious eye infection.
  • Never share your contact lenses with anyone else.
  • Avoid using temporary contact lenses that are included with costumes and aren't approved by a doctor.
  • Carry "artificial tears," a wetting solution, or glasses with you when you are likely to get dry, irritated eyes.
  • Remember that contact lenses do not offer any eye protection. Use appropriate protective eyewear when playing sports, especially hockey or squash.

Health Canada's role

Health Canada licences some medical devices, including corrective contact lenses, before they can be imported and sold in Canada. The Medical Devices Regulations require that the medical devices imported and sold in Canada are safe, effective and of quality manufacture. We do this using a combination of a pre-market review prior to licencing, and post-market surveillance of adverse events.

Related information

You can report a problem with contact lenses or any other medical device by filling in this form.

Learn more about medical devices in Canada.

For more information about eye health, visit the Canadian Ophthalmological Society.

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