The most common vision problems are: Myopia, Astigmatism,
hyperopia and presbyopia. These are called "refractive
disorders" because they have to do with how the eye bends
(refracts) or focuses light. Each of these conditions is
related to either the shape of the eye itself, the shape of
the cornea or the condition of the lens as it ages.
or "nearsightedness" is the condition of not being able to
focus at a distance while near objects may be seen clearly
even without the aid of glasses. Myopia can vary by degrees
from mild to severe. Myopia results from the shape of the
eye being too long in proportion to the curve of the cornea,
the eye's outer covering. This causes light entering the
cornea to fall short of focusing on the retina, the imaging
"screen" at the back of the eye. Imagine a film or slide
projection where the image is blurred because the light is
not properly adjusted to a focal point on the surface of the
is the term used to describe any blurring of vision
caused by a cornea that is oval shaped rather than round.
This irregular football shape causes light to enter the eye
unevenly from different angles at the same time. Light then
focuses at multiple points on, in front of and/or behind the
retinal screen. This can result in "double vision" or a
difficulty in seeing clearly at either near or far
distances. Astigmatism is often found in conjunction with
cases of myopia or hyperopia. It is the most common of focal
is the condition of not being able to focus clearly at
close range while distant objects may be viewed easily
without the aid of glasses. Hyperopia or "farsightedness"
results from the length of the eye being too short in
proportion to the curvature of the cornea. Light is not
accurately focused on the retinal screen but at a point just
beyond it, thus causing a blurring of vision close up.
Hyperopia also can vary from mild to more extreme cases.
or "old eye" is a condition of reduced elasticity of the
lens due to the normal aging process. This loss of
elasticity affects the ability of the eye to focus close up.
The condition may become evident around age 40, making
reading of small print more difficult.