Hold the book up close and the words appear blurred. Push the book farther away,
and the words snap back into sharp focus.
That's how most of us first recognize
a condition called presbyopia, a name derived from Greek words
meaning "old eye." Eye fatigue or headaches when
doing close work, such as sewing, knitting or painting, are
also common symptoms. Because it is associated with aging,
presbyopia is often met with a groan -- and the realization
that reading glasses or bifocals are inevitable
What causes presbyopia?
As we age, body tissues normally lose their elasticity. As skin
ages, it becomes less elastic and we develop wrinkles. Similarly,
as the lenses in our eyes lose some of their elasticity,
they lose some of their ability to change focus for different
distances. 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.