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Contact lenses provide a safe and effective way to correct vision
when used with care and proper hygiene. They are thin, curved plastic
disks designed to cover the cornea which is the clear front covering
of the eye. Surface tension allows contacts to cling onto the film
of tears over the cornea, the same force that causes a drop of water
to cling to the side of a glass.
Contact lenses are used to correct similar conditions that spectacles
correct including myopia (shortsightedness), hyperopia (farsightedness),
astigmatism (distorted vision) and presbyopia (old-age vision).
Special tinted contacts can be used to change the colour of the
eyes to various degrees. Contact lenses are sometimes used therapeutically
in eye diseases where an uneven cornea blurs vision, such as keratoconus
or scarring.
PMMA Lenses These rigid contacts were first developed in the 1960s.
Made of a type of plastic called PMMA which is very durable, these
lenses do not allow oxygen in the air to directly reach the cornea.
When the eye blinks, the lens moves and allows the oxygen dissolved
in the tears to reach the cornea. Although they are probably the
least comfortable type of contact lenses, some users prefer them
for their durability and lower cost.
Newer rigid plastic lenses are combined with other gas permeable
materials, such as silicone and fluoropolymers, and allow oxygen
in the air to pass directly through the lens. Gas permeable lenses
are less durable than conventional rigid lenses but are more comfortable.
Some gas permeable lenses are extended wear lenses which may be
worn overnight for up to seven days.
Majority of contact lens wearers in Singapore use soft lenses which
are made of plastic materials that incorporate water. The water
makes them soft and flexible, and allow oxygen to reach the cornea.
Some soft contact lenses are extended-wear lenses designed for overnight
use. Although these lenses are more convenient, it is preferably
not worn overnight as people who wear any type of lenses overnight
(extended wear) have a higher chance of developing infections of
the cornea.
Disposable lenses for daily or extended wear are also available
in the market recently. These lenses are discarded and replaced
weekly. They are convenient and may reduce the chance of allergic
reactions and deposit formation. Preferably, one should avoid wearing
disposable lenses overnight.
Toric lenses correct astigmatism. They are available in both rigid
and soft materials.
- Always wash hands before handling
contact lenses.
- Always cleanse and disinfect
contact lenses properly after each use.
- Clean and air-dry the contact
lenses case everyday. Wash and boil the lens case once a
week and replace the lens cases regularly.
- Follow the lens care instructions
of your eye-care professional exactly.
- Do not reuse solutions. Discard
used solutions immediately.
- Do not use home-made saline.
- Do not store contact lenses
in non-sterile fluids such as distilled water or tap water.
- Do not wear an over-aged or
damaged contact lens.
- Arrange for periodic eye examination
(at least once a year) by an eye-care professional.
- Check with your eye-care professional
or doctor before you apply any eye drops, as any eye drops,
including non-prescription ones, can interact with all types
of contact lenses.
- Remove the lens immediately
if the eye turns red or uncomfortable while wearing contact
lenses. If the problem persists, consult your eye-care professional
or doctor immediately.
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Most people who require vision correction can wear contact lenses.
However, there are certain conditions that might prevent you from
wearing contact lenses. These include dry eyes, frequent eye infections,
severe allergies, working in a very dusty environment and inability
to handle and care for the lenses.
* This is a general guide.
If in doubt, please consult your doctor.
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© 2004. Singapore National Eye Centre. All rights reserved.
