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Some types of contact lenses are especially
known for curing various vision disorders. Two of them are toric and
bifocal contact lenses. In fact, all contact lenses are used to correct
vision disorders like nearsightedness, farsightedness, astigmatism,
presbyopia and alike. Just read on to have a look at the vision
disorders corrected by these two types of contact lenses:
Toric lenses
Toric lenses were introduced in 1978 and
are used to correct the vision of patients suffering from astigmatism.
With this invention, astigmatism patients were able to wear the
disposable lenses in the late nineties. Also CIBA Vision introduced the
worlds first daily disposable toric contact lens called focus dailies
toric in the year 2002. These lenses are made with curvature at
different angles, one for astigmatism and the other for nearsightedness
or farsightedness.
It is not possible for the toric lenses to
rotate on your eye therefore, the lenses are made with a mechanism which
keeps the lens stable thus resulting in providing a crisp vision. So,
today people suffering from vision disorder like astigmatism have lots
of choices as plenty of disposable toric lenses are available including
daily, 1 to 2 week and monthly disposable lenses. Color toric lenses are
also available to change or enhance the color of your eye. These can be
both disposable and non-disposable. Presbyopia, a vision disorder can
also be corrected by using multi-focal toric lenses.
Bifocal lenses
These lenses are available since 1999 and
are used by patients suffering from a vision disorder called presbyopia.
Presbyopia is a vision disorder in which one loses the ability to read
print that is too close like a book or a menu. People with this
condition hold the reading material at an arm's length to focus on them.
This condition usually occurs around the age of 40. Presbyopia can be
corrected by bifocal lens as it has two power in one lens. Distance
vision is corrected by one part and the other part corrects the near
vision. However, there are different types designs used to create
bifocal contact lenses. These are:
A) There is an aspheric design which slowly changes the power from the
center to the edge of the lens thus allowing intermediate distance
correction.
B) A concentric design uses the center of the lens for one power and the
outside of the lens for the other.
C) A translating design includes near vision correction on the bottom and
on the top, the far vision correction. The bottom edge of these lenses
is flat to keep the lens from rotating while blinking.
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