Did you really understand what your eye doctor told you?
Care of Your Eyes © 2003-2005
by Triad Communications
(mi-OH-pee-uh), nearsightedness. Refractive error.
Focusing defect created by an overpowered eye, one that has
too much optical power for its length. Light rays scoming
from a distant object are brought to focus before reaching
the retina. Nearsighted people see close-up objects clearly
but distance vision is blurry. Corrected with a minus lens
(spectacle or contact) to "weaken" the eye optically
and permit clear distance vision.
Dictionary of Eye Terminology,
4th ed, © 2001 by Triad Communications)
An excerpt from the book Taking
Care of Your Eyes,
useful practical information about common and less-common
eye diseases and disorders, and what you can expect - from
examination through treatment, and afterward.
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. In other words, your range of clear
vision is much closer to your eyes than if you weren't nearsighted.
Approximately 40% of the population has some 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" are happy to be able to see things clearly
up close without glasses. In fact, this ability can be a real
advantage, especially after middle age.
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,
this does not necessarily mean they are nearsighted. It may
only mean that they like the way things look up close.
Sharp vision -- like the picture from a properly focused camera
-- depends on light rays coming to a focus on the retina (at
the back of the eye), just as light focuses on the film (at
the back of a camera). When light rays do not come to a focus
on the retina, vision will be blurred, and we say that a refractive
(optical) error exists.
is just one type of refractive error. The others are hyperopia
(farsightedness), astigmatism (uneven focusing), and presbyopia
(the inability to focus up close, which affects most people
around middle age). 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
foot size or tallness. The myopic eye is larger or elongated
- too long for its optical power - which means its optical
power too strong for the eye. (You shouldn't think of nearsightedness
as "weak eyes.") Research 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 hurt your eyes by
populations (the Inuit eskimos, for example) have shown a
statistical shift toward myopia when, over many years, some
members of their society changed from outdoor activity to
working inside, doing much closer work. This fact, however,
does not mean that if an individual does a lot of close work,
he or she will become myopic.
from heredity, there 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 my
occur 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 becomes cone-shaped.
Does Myopia Get "Worse" as the Child Gets Older?
children's bodies grow, so do the eyes, which may cause a
gradual increase in myopia. And just as bodily growth can
be in uneven spurts, the changes in myopia may be similarly
uneven. During adolescence, the change can be rather rapid
and require a new, thicker eyeglass correction more than once
a year, but when body growth slows or stops (usually by age
18), the myopia tends to stabilize. There is normally no reason
to worry about the frequent changes in lens correction that
occur during adolescence. Almost never is there 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 type of myopia, called malignant
progressive myopia, which is a serious condition and leads
to gradual structural damage to the eye. This type needs regular
clinical evaluation. It is not related to ordinary myopia
and does not develop from ordinary myopia.
Correction for Myopia
eyeglasses or contact lenses provide a simple, effective way
to provide clear vision - by optically reducing the excess
power of the myopic eye. Wearing your correction will make
your 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,
of course, 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, but the safest ones
for active people are made of polycarbonate plastic. These
offer the best possible protection against eye injuries.
Methods of Correction
is some evidence that special contact lenses (in a procedure
called orthokeratology), bifocal eyeglasses, or dilating eyedrops
can be used to 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 being well publicized as the modern way to reduce
your dependence on glasses or contacts. This type of surgery
includes several procedures for permanently lessening or possibly
even eliminating myopia. Some involve using an excimer laser
to reshape the cornea (PRK, LASIK); one uses a surgically
implanted plastic corneal ring (the effect is reversible if
the ring is removed). All are intended to reduce the cornea's
optical power to achieve normal or near-normal focus. These
procedures are not appropriate for everyone, and are not done
on a young eye that is still growing. Before making a decision
to have refractive surgery, you should learn all you can about
it and the different procedures that are available.
Care of Your Eyes ©
2003-2005 by Triad Communications.