Eye Glasses and Contact Lenses
Lenses for correcting or improving vision:
There are two types of lenses prescribed for
correcting or improving vision. These include:
- eyeglasses
(Also called spectacles.)
Eyeglasses, the most common form of eyewear used to
correct or improve many types of vision problems, are
a frame that holds two pieces of glass or plastic,
which have been ground into lenses to correct
refractive errors. Refractive errors can include
nearsightedness or myopia (difficulty seeing far away),
farsightedness or hyperopia (difficulty seeing close
up), and astigmatism (blurring due to an irregularly
shaped cornea). Eyeglasses perform this function by
adding or subtracting focusing power to the eye's
cornea and lens.
- contact
lenses
Contact lenses are worn directly on the cornea of
the eye. Like eyeglasses, contact lenses help to
correct refractive errors and perform this function by
adding or subtracting focusing power to the eye's
cornea and lens.
How to read an eyeglass prescription:
The lens power of eyeglasses is measured in diopters.
This measurement reflects the amount of power necessary
to focus images directly on to the retina. When looking
at an eyeglass prescription, you will see the following
abbreviations:
O.D. - Oculus dextrus simply refers to the right
eye (sometimes the abbreviation RE is used).
O.S. - Oculus sinister refers to the left eye (sometimes
the abbreviation LE is used).
In addition, the eyeglass prescription may also
contain the following measurements:
- sphere
- this number measurement reflects the extent of the
nearsightedness or farsightedness.
- cylinder
- this number measurement refers to the amount of
astigmatism (an irregularly shaped cornea which causes
blurring) in the eye.
- axis - this number measurement describes
the direction of the astigmatism in degrees.
Bifocal is additional power in the lens and has an
additional measurement listed on the prescription as "add,"
to indicate the strength of the lens.
What are the different types of eyeglass lenses?
The type of lenses used in eyeglasses depends on the
type of vision problem, and may include:
- concave lenses - are thinnest in the
center. Used to correct nearsightedness (myopia), the
numerical prescription in diopters is always marked
with a minus (-) symbol.
- convex lenses - are thickest in the center,
like a magnifying glass. Used to correct
farsightedness (hyperopia), the numerical prescription
in diopters is always marked with a plus (+) symbol.
- cylindrical lenses - curve more in one
direction than in the other and are often used to
correct astigmatism.
Eyeglasses for children:
If old enough, let your child play an active role in
choosing his/her own glasses. The following are features
to consider when buying eyeglasses for children:
- shatterproof and impact resistant lenses -
especially for children who participate in sport
activities
- scratch-resistant coating on the lenses
- spring-loaded frames that are less likely to be
bent or warped
- silicone nose pads that prevent glasses from
slipping
- cable temples (ear pieces that wrap around the ear)
- recommended in children under 4 years. Straps may
also be recommended to hold the glasses in place.
Facts about contact lenses:
Almost 30 million Americans wear contact lenses, half
of whom wear daily wear soft lenses. Currently, there
are five types of contact lenses in use, including the
following:
- the original "hard" lens
- the rigid, gas-permeable lens
- other rigid lenses
- the soft, water-absorbing lens
- other flexible, non-water absorbing lenses
Reading a contact lens prescription:
The prescription for contact lenses includes more
information than what is available on the prescription
for eyeglasses. Special measurements are taken of the
curvature of the eye. In addition, your child's
physician will determine if the eyes are too dry for
contact lenses, and if there are any corneal problems
that may prevent a person from wearing contact lenses.
Trial lenses are usually tested on the eyes for a period
of time to ensure proper fit.
The contact lens prescription usually includes the
following information:
- contact lens power (measured in diopters, like
eyeglasses)
- contact lens base curve
- diameter of the lens
Eye care specialists are required by federal law to
give you a copy of your contact lens specifications.
Protect your child's eyes from the sun:
Although parents go through great lengths to protect
their children's skin from the harmful rays of the sun,
many forget that the eyes need to be protected, too.
Nearly half of American parents do not regularly provide
their children with sunglasses that protect their eyes
from the sun's ultraviolet (UV) rays. Exposure to sun
may set children up for potential vision problems later
in life.
The sun can cause sunburned corneas, cancer of the
eyelid, cataracts, and macular degeneration, among other
problems. In addition, children are more susceptible
because their lenses do not block as much UV as adult
lenses. Children also tend to spend more time outdoors
than their parents, often in places where there is a lot
of sun reflection - beaches, pools, and amusement parks.
Most UV eye damage is cumulative.
Protecting a child's eyes from the sun is simple:
