from Triad's Eye Care Notes
© 1989-2005 by Triad Publishing
When you are nearsighted (myopic), your vision is clear for
objects close to your eyes, but blurred for everything in
the distance. If a child cannot see the blackboard clearly
from the back of the classroom, chances are that he or she
comes in all degrees, from minimal to extreme. The more myopic
you are, the more blurred your distance vision, but the closer
up you can see clearly -- your range of clear vision is closer
to your eyes than if you weren't nearsighted. About 40% of
the population has some degree of myopia or will develop it
at some time in their lives.
commonly, myopia begins to appear gradually between the ages
of 8 and 12, though it can exist at birth or start to develop
as late as age 80. Myopia may be a nuisance but it is certainly
not a disease; most nearsighted people have perfectly healthy
eyes. Many "myopes" really like being able to see clearly
up close without glasses. In fact, this ability can be a real
advantage, especially after middle age.
The only symptom of myopia is blurred vision for distant objects.
Eye fatigue, burning eyes, headache, and limited tolerance
for reading occasionally accompany the myopia, but they are
not symptoms of the myopia itself. When young children hold
everything close to their face or sit very close to the television,
it does not necessarily mean they are nearsighted -- they
may simply like the way things look up close.
a properly focused camera, light focuses on the film at the
back of the camera, and a sharp, in-focus picture is taken.
In the same way, sharp vision depends on light rays coming
to a focus on the retina (at the back of the eye). When light
rays are not focused sharply on the retina, vision will be
blurred, and we say that a refractive (optical) error exists.
In myopia, the rays from distant objects focus in front of,
rather than on, the retina. Myopia is like a camera that is
in focus only for near objects; anything in the distance is
out of focus.
most cases, myopia is the result of a size variable, like
height or foot size. A myopic eye is elongated, and its length
doesn't coordinate with its optical power; in other words,
its optical power is too strong for the eye. (You shouldn't
think of nearsightedness as weak eyes.)
suggests that ordinary myopia and how fast it progresses during
adolescence are determined by heredity: it tends to run in
families. It is not caused by using your eyes "too much" (you
never harm your eyes by using them). Some populations, the
Inuit (eskimos), for example, have shown a statistical shift
toward myopia when, over many years, they changed from outdoor
activity to closer work indoors. This does not mean that doing
close work will make a person myopic.
are a few less common causes. Myopia that appears (or increases)
in middle age may be a sign of a beginning cataract. In uncontrolled
diabetes, myopia may appear suddenly and then change erratically
from day to day. And rarely, a teenager may develop myopia
from keratoconus, an unusual condition in which the cornea
gradually becomes cone-shaped.
Does Myopia Get "Worse" as the Child Gets Older?
children's bodies grow, so do their eyes, which may cause
a gradual increase in myopia. And just as bodily growth can
be in spurts, the changes in myopia may be similarly uneven.
During adolescence, the change can be rather rapid and require
a stronger eyeglass correction more than once a year, but
when body growth slows or stops (usually by age 18), the myopia
tends to stabilize.
is normally no reason to worry about the frequent changes
in lens correction during adolescence. There is almost never
any real danger to eyesight, and vision can almost always
be corrected to 20/20 or better with eyeglasses or contact
lenses. (There is an extremely rare and serious type of myopia,
"malignant progressive myopia," that leads to gradual structural
damage to the eye. But this type is not related to nor does
it develop from ordinary myopia.)
Correction for Myopia
or contact lenses provide a simple, effective way to attain
clear vision. By optically reducing the excess power of the
myopic eye, they make distance vision clear. The more nearsighted
you are, the more you will want to wear your correction. Not
wearing it, however, will not harm your eyes in any way.
children should be checked for glasses every year or so, and
nearsighted adults every 2 to 3 years -- more frequently if
you start having any symptoms that seem to be related to your
eyes. For eye safety, impact resistant lenses are required
by law for all eyeglasses. The safest ones, offering the best
protection against eye injuries, are made of polycarbonate
Methods of Correction
is some evidence that special contact lenses (in a procedure
called orthokeratology), bifocal eyeglasses, or dilating eyedrops
can slow the progression of myopia, but the effects are very
minimal and temporary, and rarely worth the extra effort and
cost. Treated or not, myopia almost always advances to a certain
point and then stops changing.
surgery is an option for reducing your dependence on glasses
or contacts. These surgical procedures are designed to permanently
reduce the optical power of the cornea to achieve normal or
near-normal focus. LASIK and PRK involve use of an excimer
laser to reshape the cornea. Intacs are surgically implanted
corneal ring segments that flatten the cornea; the effect
is reversible by removing the rings. Refractive surgery is
not appropriate for everyone, and it is not done on young
eyes that are still growing. Before making a decision to have
refractive surgery, you should learn all you can about it.
from Triad's Eye Care Notes
© 1989-2005 by Triad Publishing Co.
Patients: for more information about your eyes, see: Taking
Care of Your Eyes: A Collection of the Patient Education Handouts
Used by America's Leading Eye Doctors