contact lenses

系統文章 類別:英文 時間:2010-07-01 00:00:00
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Many short-sighted women wear contact lenses because they think they are more
attractive than spectacles. Some also think that vision feels more natural with
contact lenses. However, contact lenses are not suitable for everyone.
People suffering from high blood pressure are better off avoiding contact
lenses, whilst those with arthritis may have trouble handling contact lenses
and placing them in their eyes. A bad environment filled with sandy wind,
powder, dust, or volatile chemicals in the air can be dangerous for contact
lens wearers. Lazy bones and kids are also unsuitable candidates for contact
lenses since they require more care than glasses. Contact lenses on the market
can be categorized to two types: hard contact lenses and soft ones. The hard
ones, which are also called rigid contact lenses, are thin disks made of hard
plastic. Gas-permeable lenses, made of silicone and other compounds, are rigid
but permit better oxygen transport to the cornea. Soft ones can be divided to
soft hydrophilic ones and nonhydrophilic. Soft hydrophilic contact lenses, made
of flexible plastic are larger and cover the entire cornea. Most soft,
nonhydrophilic lenses are made of silicone. People may find soft lenses easier
to handle because they're larger. They are also less likely than rigid lenses
to fallout or to allow dust and other particles to get trapped underneath.
Plus, soft contact lenses are unusually comfortable on the first wearing. They
do, however, require scrupulous care. For the new wearer, contact lenses may
be uncomfortable, they shouldn't be painful. Pain indicates an improper fit.
Extended wear enables people to wear them for several days without removing
them. However, for the sake of health, doctors advise people to choose daily
wear rather than extended wear. Your room needs airing, by opening windows
frequently, and your eyes also need airing by removing your contact lenses
every day. Wearing any kind of contact lenses poses the risk of several
complications, including cornea ulceration from an infection that may lead to
a loss of vision. No venture, no gains. Before you set your mind to replace
your eyeglasses with contact lenses, take these risk to considerate and then
figure out if the benefits outweigh the risks. If a wearer of contact lenses
experiences discomfort, excessive tearing, vision change or eye redness, lenses
should be removed immediately. If the symptoms don't resolve quickly, the
person should consult an eye doctor.