Astigmatism is a common type of visual problem that
partly blurs an image. This is because there is
irregularity in the curve of the front surface of the eye
(the cornea). The cornea is curved more like a football (an
American football, that is) or a rugby ball rather than the
normal shape of a spherical basketball.
Light rays entering the astigmatic eye are not uniformly
focused on the retina. Rays going through the more-curved
surface are focused in front of the rays coming through the
The light is focused clearly along one plane but is
blurred along the other. The result is blurred vision at
all distances. Only part of what an individual with an
astigmatism is looking at is in clear focus at any given
Astigmatism may be so slight that it causes no problems.
Almost everyone has some degree of astigmatism.
Moderate astigmatism can cause headaches and eye strain.
Severe astigmatism can seriously blur vision. Astigmatism
can contribute to poor school performance but paradoxically
it is usually not detected during routine eye screening in
Astigmatism is a refractive error. It may be present
along with other problems in refraction, such as near-
sightedness or far-sightedness.
Astigmatism is corrected with slightly cylindrical
lenses that have greater light-bending power in one
direction than the other. These lenses elongate objects in
one direction and shorten them in the other, much like
looking into a wavy mirror at a circus.