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How strong is a polycarbonate
lens? The photo at the left gives some idea.
A nail has been hammered through the lens, and it is now
anchored in the lens. The lens has not shattered or cracked as
might be expected.
Polycarbonate is used in many applications
requiring great flexibility
and strength,
such as "bullet proof" windows and safety lenses. Some of
polycarbonate's other properties make it an excellent choice
for regular glasses as well. |
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Courtesy of
Elvex Corp. |
For maximum impact resistance,
polycarbonate is the obvious choice. Polycarbonate lenses are ten
times more impact resistant than conventional plastic or glass
lenses. While impact resistant does not mean shatterproof,
polycarbonate lenses can give an extra level of protection to lens
wearers who have active lives or participate in sports.
Polycarbonate is the material preferred for children and teenagers,
as well as people who work in hazardous manufacturing occupations.
The basic polycarbonate material is
quite soft which is why the material can absorb so much impact. When
used for eyeglass lenses, polycarbonate always includes a tough,
scratch-resistant coating applied to both sides of the lens. This
coating provides protection against normal handling scratches
Developed originally for the
aerospace industry, polycarbonate is used in the windows found in
airliners and face plates in astronauts' helmets. The helmets used
by baseball and football players are also made from polycarbonate.
Other Advantages
Polycarbonate lenses are thinner and lighter
than conventional plastic or glass lenses. Polycarbonate was the
first plastic "high index" lens material.
High-index materials are useful because they bend light more - so
less material is needed to create a given prescription.
Long-term exposure to ultraviolet
light (especially UV-B) is thought to increase the risk
of cataracts and damage to the retina. Wearing
a pair of sunglasses that absorbs visible light but NOT ultraviolet
light is probably more damaging than not wearing sunglasses at all -
because sunglasses leave the wearer less conscious of the dose of
ultraviolet he is receiving. Polycarbonate lenses have
built-in ultraviolet protective properties. Just as sunblock can
help prevent the sun from damaging your skin, polycarbonate's
built-in UV protection can help prevent damage to your eyes.
The
frame makes a difference!
Using
a "dress" frame with polycarbonate lenses is fine when your primary
goal is to create thinner, more cosmetically appealing lenses.
When your goal is eye protection for sports, remember
that the frame is all that anchors the lenses at a safe distance in
front of your eyes. A frame that is stylish but not made from
durable materials, greatly reduces the safety advantages of
polycarbonate. Try to choose a frame that provides greater facial
coverage and deeper grooves for holding the lenses in the frame.
Frames with thin eyewires (part of frame surrounding lenses) usually
have shallower lens grooves. If your lenses are impacted, a frame
with thicker eyewires and deeper lens grooves is simply more likely
to hold the lenses in place.
Polycarbonate lenses can protect eyes from
many hazards in the workplace or at home, but if they are placed in
a frame that is not safety rated, they may not provide adequate
protection. If glasses are to be used in the workplace, the law
requires that certain standards are met; the term safety "glasses"
refers to the frame just as much as it does to the lenses.
In conclusion:
Always wear appropriate protective eyewear when participating in
activities such as baseball, basketball, hockey, lacrosse, football,
soccer, paintball and racquet sports.
In addition to being the most shatter
resistant material available, polycarbonate is also thinner and
lighter than standard plastic, so it improves the appearance of most
prescription lenses. Whether used for dress or sports eyewear,
polycarbonate has some definite advantages. The next time you visit
your eye doctor, be sure to ask if lenses made from polycarbonate
would be a good choice for you.
New pricing now allows us to provide you with Daily Disposables at simliar prices as the BiWeekly and Monthly Lens. Call our office for details.
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Vision and Health Newsletter courtesy of:
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Dr. Philip Smith & Associates
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1855 1st Ave #100
San Diego, CA 92101
619-297-4331 |
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