Here is a Glossary of Terms Relating to Vision:
(you can find out more in the Vision Links Page)
What is Myopia?
Myopia, or "nearsightedness",
is a common vision problem. It is caused by the inability of light to focus
on the retina because the eye is either too long or the curvature of the
cornea is too steep. If either of these conditions exists, light focuses
in front of the retina and the image on the retina is blurry. Glasses and
contact lenses correct myopia by bending light rays in such a way that
the rays focus on the retina.
What is Hyperopia?
Hyperopia or "farsightedness"
is a condition in which the eye is too short or the curvature of the cornea
too flat for light to focus on the retina. Instead, light, if it could,
would focus behind the retina. The result of this is a blurry image on
the retina. Unlike myopia, under certain conditions the eyes can compensate
for small amounts of hyperopia and so often people that are farsighted
may not feel like they need glasses or contacts because they can see objects
clearly. As with myopia, contact lenses and glasses correct hyperopia.
What is Astigmatism
Astigmatism occurs when the
cornea (the clear part at the front of your eye that provides most of the
focusing power of the eye) is oval instead of round. The best analogy is
to think of an eye with astigmatism being shaped like a football and an
eye without astigmatism being shaped like a basketball. Because of the
oval shape of the cornea light rays are bent unevenly causing a distorted
image. Glasses and contact lenses correct astigmatism.
What is Presbyopia?
Presbyopia is the condition that everyone dreads which usually presents around age 40. It is the need to wear reading glasses or bifocals when focusing on objects that are close. It is caused by the natural changes that occur in the lens of the eye. As we get older, the lens starts to lose it's ability to change shape and thus it loses the ability to change focus. As mentioned earlier, presbyopia is corrected with reading glasses, bifocals, or contact lenses. Many people falsely believe that once they reach the point of needing reading glasses they can no longer wear contact lenses. There are several contact lens options available to presbyopes. Contact your optometrist for more information.