For someone without astigmatism, the eye is shaped like a basketball.
When an individual has astigmatism, the surface of the eye is curved
more like a rugby ball, with both flatter and steeper curves.
Astigmatism distorts or blurs vision for objects at any distance.
Blurry vision from astigmatism is similar to the effect of "funhouse"
mirrors in which you appear too tall, too wide, or too thin. Large
amounts of astigmatism are usually inherited, may be present at birth,
and frequently remain unchanged throughout life. Small amounts of
astigmatism are very common and may be acquired any time in life which
often do not require correction with glasses or contact lenses.
Treatment:
Correction of astigmatism is not difficult if the distortion proceeds
in a regular direction across the cornea. A similar but opposite curve
can be made in prescription glasses to neutralize or offset the distortion
of the cornea. However, if the cornea has been injured or scarred,
the corneal distortion may be irregular. So-called irregular astigmatism
is more difficult to correct and can by improved only by reshaping
the corneal surface. This may be accomplished either by wearing a
hard contact lens, or by performing a corneal transplant, which involves
removing the scarred cornea and replacing it with donated human corneal
tissue.
Hard or gas-permeable contact lenses improve astigmatism better than
soft contact lenses, but special soft contact lenses which correct
mild astigmatism are sometimes helpful. If the amount of astigmatism
is very large, glasses that correct the condition may cause some diction
of peripheral vision. Very large amounts of astigmatism are not easily
corrected with a contact lens, since the lens may wobble on the wavy
surface of the cornea. In such instances, a special toric contact
lens may be ground with a curve in the back surface to stabilize the
lens on the cornea.
