The
Normal Eye
In order to see clearly, objects need to be brought to a focus
point precisely on the retina of the eye. The retina can be
compared to the film in a camera. The light is brought to a focus
point by the cornea and lens of the eye. The cornea's curvature is
ideally matched to it's length in the normal eye. As the normal
eye ages, the lens loses the ability to focus for reading and will
require the help of reading glasses. This usually begins to affect
most people after the age of 40
The
Near-Sighted Eye
If you are nearsighted, the cornea of your eye is overly curved
or your eyeball is too long. This combination brings images of
distant objects (street signs) to a focus point in front of the
retina. When the light reaches the retina, a blurred image is
seen since the light rays spread apart after the focus point.
The
Far-Sighted Eye
If you are farsighted, the cornea of your eye is not curved
enough or your eyeball is too short. This combination of factors
causes the focus point of the eye to be located behind the
retina. When light reaches the retina, a blurred image is seen
since the light rays have not been brought to focus prior to
reaching the retina.
The
Astigmatic Eye
If you have astigmatism, the cornea of your eye has a
non-spherical shape (like a football) and does not bring light
to focus at a single point. Instead, it focuses images over a
range of points producing a blurred image. Both nearsighted and
farsighted eyes can also have astigmatism.
