The Issue

The Issue
It’s Your Health
The Issue
Contact lenses are medical devices which,
like drugs, provide benefits while posing
certain risks. If you wear contact lenses, you
should take steps to minimize these risks and
protect your vision.
Many people wear contact lenses to correct
their vision. The reasons for choosing
contacts 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
improved vision correction when compared to
glasses because they correct the refractive
error closer to the eye. 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
a higher percentage of 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 by bacteria,
dust and protein. Usually soft contact
lenses are removed from the eye 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
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, and are more
effective for people with astigmatism.
Cosmetic contact lenses are tinted lenses
that are used purely for cosmetic reasons to
change the colour of the eye.
Corneal reshaping or refractive lenses are
rigid gas permeable contacts 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 and astigmatism in
adults. These lenses do not correct vision
while they are worn. Instead, vision is
corrected for several hours after wear, because
the cornea has been temporarily reshaped
during sleep. The procedure is called
orthokeratology, and the results are variable.
This type of contact lens should be fitted only
by an eye care professional with specialized
Potential Adverse Health
The most common eye problems
encountered by contact lens users are excess
tearing, itching, burning, sensitivity to light,
dryness, and occasional blurred or distorted
vision. These conditions may be worsened
by improper care or cleaning of contact
lenses and increase the risk of developing an
eye infection.
Clinical studies suggest that the extended
use of contact lenses, particularly overnight,
seriously increases the risk of
developing corneal ulcers. This condition
is called ulcerative keratitis. An ulcer
can perforate or scar the cornea in a
day or two, leading to permanent
scarring of the cornea or even
blindness. Many eye doctors advise
their patients not to use extended-wear
contact lenses.
Smokers are eight 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 antihistamines, birth control
pills, alcohol and air travel, can
make contact lenses uncomfortable,
and can increase the risk of an eye
infection. In addition, environmental
contaminants, such as dust, smoke,
sprays and pollen, can irritate the
eyes when you wear contacts.
Minimizing Your Risk
The most important step you can
take is to have your contact lenses
prescribed and fitted by a qualified
eye care professional. You should
also participate fully in the follow-up
care that is recommended, and:
• Read all of the patient
information pamphlets that come
with your contact lenses.
• Clean and care for your contacts
as recommended by your eye
care professional.
• Wash your hands thoroughly
before handling your contacts.
• Do not use tap water or saliva to
clean contacts.
• Preservatives used in contact
lens solutions may become
irritating. If this happens, consult
your eye care professional. Do
not switch brands of contact lens
solutions on your own, as this
Original: October 2003
It’s Your Health
may lead to more toxic reactions
or irritation.
• Do not wear your lenses for a
longer period of time than
recommended by your eye care
• Bear in mind that overnight wear
of contact lenses, including
extended-wear contacts, is
associated with an increased risk
of serious eye infection.
• Never share your contact lenses
with anyone else.
• Avoid using temporary lenses
that are included with costumes
and are not approved by a
• 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.
In summary, if you experience
blurred or hazy vision, or develop a
pain in your eye while wearing contact
lenses, remove them 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.
Health Canada’s Role
Medical devices, including corrective
contact lenses, must be licenced by
Health Canada 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. This
is achieved by a combination of a
pre-market review prior to licencing,
and post-market surveillance of
adverse events.
Non-corrective colour contact lenses
or cosmetic contact lenses are not
considered to be medical devices in
Canada as they do not correct or
modify a body function or structure.
Therefore, you do not need a
prescription to buy them. Non-corrective
colour contact lenses are currently
managed by the Cosmetics
Division. Manufacturers and
importers must notify Health Canada
that they intend to market the
product, and are required to provide
safety data.
Need More Info?
To report problems with contact
lenses or any other medical
device, call Health Canada’s
Medical Devices Hotline,
1-800-267-9675 (toll-free in Canada).
For more information on medical
devices, visit:
For more information on contact
lenses go to the Canadian Health
Network at:
and search for "contact lenses"
For more information about eye
conditions, disorders and treatments,
visit the Canadian Ophthalmologist
Society’s Web site at:
Additional It’s Your Health articles
can be found at:
You can also call (613) 957-2991
ISBN# H50-3/123-2003E-PDF
Catalogue # 0-662-35396-X
©Her Majesty the Queen in Right of Canada, represented by the Minister of Health, 2004
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