Wednesday, January 28, 2009

Contact lenses and your eyes' health

Contact lenses and your eyes' health

Do you wear contact lenses? If so, there are things you should be aware of, to protect your eyes from permanent damage.            

Contact lens eye

In a nut shell: give your eyes a break. Expert say that you can get away with wearing contact lenses 12 to 14 hours a day, but that you should give your eyes a break once a week. Most experts agree that if someone wears contact lenses for too long - say for over 16 hours/day each day - their eyes could become starved of oxygen. In the long-term, this can result in the cornea losing its transparency.

If your eyes get starved of oxygen, tiny blood vessels in the eye start to shoot off and new ones develop. The most disturbing thing about blood vessels growing on the eye is that there are usually no symptoms and the eye could feel perfectly normal. An optician will be on the look out for signs of this happening, and so it is a good idea to have your eyes examined by an optician regularly.

According to a Dutch study (1), overnight use of extended-wear contact lenses is the most important risk factor for a potentially blinding form of eye infection, called "microbial keratitis".


The researchers focused on the incidence of this rare form of bacterial eye infection associated with contact lens use. In certain rare cases, microbial keratitis can result in damage to the cornea leading to partial or total blindness in the eye.

According to the researchers in this study (1), the risk of microbial keratitis was almost 20 times greater for users of extended-wear soft contact lenses and 3 times greater for users of daily-wear soft contact lenses than for people who use daily-wear hard lenses. The researchers attribute the high risk of infection of extended-wear lens users to the users' tendency to keep the contact lenses in overnight.

Hard or soft contact lenses?

The old type of hard contact lenses were made from a material that did not allow any oxygen to get through to the cornea, therefore tiny holes had to be made in them. Then the rigid gas permeable contact lens was developed, which allowed more oxygen to get through.

Today's rigid gas permeable contact lenses are generally referred to as "hard" contact lenses. Hard contact lenses can be useful if you suffer from astigmatism (egg-shaped eye) because they can be moulded in order to correct the egg-shape.

Soft contact lenses, are made from gel-like plastics, are all gas permeable, and come in many different levels of water-content, which allows different levels of oxygen to reach the cornea. Most people choose soft lenses over hard contact lenses because they are generally more comfortable. But in some cases hard lenses are still preferable.

Once I get my contact lens prescription from my optician, I usually prefer to buy my contact lenses online as this is usually a cheaper alternative. I get the contact lenses recommended by my optician, only for less money than the doctor charges usually. The laws were changed some years ago to allow contact lens customers the freedom to buy their contact lenses where they wish. If your eye doctor refuses to give you a copy of your prescription, find another eye doctor.

What about eye drops and contact lenses?

When you use a computer for an extended period of time, for example, you tend to blink less. Your eyes are open for longer, therefore more tears evaporate and your contact lenses dry up faster. This situation can be made worse by centrally heated or dry air-conditioned offices.


            For this reason, it is a good idea to use eye drops a few times a day. Make sure your bottled eye drops are fresh, since although eye drops contain preservatives, they usually need to be used within 30 days, although most people have a tendency to keep them for a couple of years.

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