How do contact lenses correct vision?
Contact lenses are designed to rest on the cornea, the clear outer surface of the eye. They are held in place mainly by adhering to the tear film that covers the front of the eye and, to a lesser extent, by pressure from the eyelids.
As the eyelid blinks, it glides over the surface of the contact lens and causes it to move slightly. This movement allows the tears to provide necessary lubrication to the cornea and helps flush away debris between the cornea and the contact lens.
Contact lenses are optical medical devices, primarily used to correct myopia, hyperopia, astigmatism and presbyopia. These conditions prevent an image from focusing properly on the retina, the thin layer of tissue that lines the inner posterior portion of the eye. When light is not focused properly on the retina, the result is blurred or imperfect vision.
When in place on the cornea, the contact lens functions as the initial optical element of the eye. The optics of the contact lens combine with the optics of the eye to properly focus light on the retina. The result is clear vision.
Would you like an alternative to wearing glasses?
- Are there special occasions when you would prefer not to wear glasses? Do you find glasses get in the way when you play sports? Contact lenses can be used intermittently — for special occasions, while participating in sports or to match your fashion style – while glasses may suit your every day needs better for activities like work or school.
- Single-use, one-day disposable contact lenses are comfortable and easy to use. They do not require cleaning, you simply throw them away daily after each use.
Contact lens wear may not be recommended if:
- Your eyes are severely irritated due to ocular allergies;
- You work in an environment with lots of dust and chemicals;
- You have an overactive thyroid, uncontrolled diabetes, or severe arthritis in your hands; or,
- Your eyes are overly dry due to a medical condition, pregnancy or medications you are taking.
After a thorough eye examination, we can determine your suitability for contact lenses and the specific contact lens options that best meets your requirements.
What are the advantages of wearing contact lenses?
- Wearing contact lenses allows people to see your eyes better. Some people don’t like their appearance in eyeglasses.
- Contact lenses may allow better vision correction due to the reduced obstruction from eyeglass frames.
- They provide excellent peripheral vision.
- They don’t fog up when you come in out of the cold.
- They don’t get splattering during rain showers.
- They don’t get in the way during sports and other recreational activities.
What are the disadvantages
- Contact lenses require adaptations. New soft lens wearers typically adjust to their lenses within a week. Rigid lenses generally require a longer adjustment period.
- Except for some daily disposable varieties, almost all lenses require regular cleaning and disinfection, a process that, although requiring only a few minutes a day, is more than some people are willing to undertake.
- Contact lenses have to be inserted and removed on a daily basis.
Your Doctor of Optometry will need to know: what kind of lifestyle you lead? What kind of work do you do?
- For those involved in sports and recreational activities, contact lenses offer a number of advantages. In addition to providing good peripheral vision, eliminating the problem of foggy or rain splattered lenses, and freeing you from worries about broken glasses, contact lenses also mean you can wear non-prescription protective eye wear.
- Looking sideways through the lenses of glasses leads to prismatic effects because you are not looking through their optical centers. Your eyes have to coordinate differently to cope with this. This does not happen with contact lenses because you always look through the optical center of the lenses as they move with your eye movements.
- Your occupation and work environment should also be taken into consideration. People whose work requires good peripheral vision may want to consider contacts. Those who work in dusty environments or where chemicals are in heavy use are likely to find spectacles more comfortable and safer.
Purchasing Contacts Online
Purchasing contact lenses online comes with risks to your vision and eye health. It is important to remember that every contact lens product is unique and designed for a particular purpose. This includes everything from material, curvature, fit, oxygen permeability, deposit resistance, moisture content and lifespan.
Use only the care system and solutions recommended by your Doctor of Optometry. You should see your Doctor of Optometry yearly to monitor the health of your eyes and to receive a personal consult on your contact lens needs. Also, seek immediate care if you experience any discomfort or vision changes.
Please be advised: just because you have a prescription (new or old) does not mean you will get the appropriate product for your unique ocular characteristics, unless you get it from your eyecare professional. Contact lenses are medical devices that sit directly on your corneas and can cause problems if improperly fit or not correctly monitored.
There are a number of risks associated with online ordering:
- Some sites do not verify the prescription. Without proper verification, you risk wearing an optically incorrect or improperly fitting lens.
- Many online sites (including those based in Canada) sell products that have not been approved by Health Canada. The safety of these lenses has not been tested.
- Lenses from overseas may be exposed to large temperature changes in uncontrolled warehouses or transportation vessels. This can affect the integrity of the lenses that can lead to potential eye health issues.
- Overseas distribution channels may have grey market (counterfeit) product. There are no controls to ensure that Internet sites source lenses directly from the manufacturer.
- Replacement and exchange privileges may not be available with an online vendor.
- By working with your Doctor of Optometry, you can ensure:
- The proper contact lens prescription, curvature, and modality based on lifestyle needs, and measurements of your eye curvature, tear chemistry and prescription.
- The appropriate selection of a care system and solutions based on compatibility with different lens materials and compatibility with your eyes.
- Professional monitoring to ensure optimum eye health, good vision and comfortable wear.
- Updates with new lens technology that may better suit your particular vision needs or lifestyle demands.
Source: adopted from the Canadian Association of Optometrists website