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The loss is gradual. Long before we
become aware that seeing close up is becoming more difficult, the
lenses in our eyes have begun losing their ability to flatten and
thicken. Only when the loss of elasticity impairs our vision to a
noticeable degree do we recognize the change.
Recent
research suggests that presbyopia occurs when the lens keeps growing
as people get older and the ligaments become too slack for the muscles
to work properly. This finding contrasts with the traditional view
that aging cause the focusing muscles to become weaker and the lens to
become more inflexible.
How does the
loss of elasticity affect sight?
The crystalline lens plays a key role in focusing light on the retina.
When we are young, the lens is flexible. With the help of tiny ciliary
muscles, it changes shape, or accommodates, for both near and distant
objects by bending or flattening out to help focus light rays. As we
age, the lens becomes stiffer. Changing shape becomes more difficult.
Not only does focusing on near objects become more difficult, the eye
is also unable to adjust as quickly to rapid changes in focus on near
and distant objects.
The
flexibility of the lens begins to decrease in youth. The age at which
presbyopia is first noticed varies, but it usually begins to interfere
with near vision in the early 40's. Presbyopia affects everyone and
there is no known prevention for it.
How is the
problem diagnosed and treated?
An accurate, thorough description of symptoms and a comprehensive eye
health examination, including a testing of the quality of your near
vision, are necessary to diagnose presbyopia.
Usually,
the treatment for presbyopia is prescription eyeglasses to help the
eye accommodate for close-up work. Prescription lenses (reading
glasses) help refract light rays more effectively to compensate for
the loss of near vision.
If you do
not have other vision problems, such as nearsightedness or
astigmatism, you may only need glasses for reading or other tasks
performed at a close range. If you have other refractive errors, such
as nearsightedness, bifocal or progressive addition lenses (in which
the power of the lens changes gradually towards the bottom to allow
reading, without the reading portion of the bifocal lens being
obviously visible) are often prescribed.
Can I still
wear contact lenses?
Yes, you have three options with contact lenses: Bifocal contact
lenses, monovision, and normal distance contact lenses with reading
glasses. Generally, bifocal contact lenses are not as successful as
the normal "single vision" ones.
What lens
option will work best for me?
You will be asked a number of questions about your usual lifestyle or
daily activities - to help determine the solution most suited to your
needs. For instance, if you are a librarian, your needs will be
significantly different from those of a truck driver or office worker.
Presbyopia is a gradual change, happening over a number of years so
your prescription will need to be updated periodically. Changes are
best made at your regular eye examination rather than after the need
for change starts to cause you difficulties.
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