refers to a condition of the focusing system, wherein
the focus point of the eye is in more than one place. This
condition blurs and distorts both distant and near objects.
If you have astigmatism, your cornea is shaped more like the
back of a spoon, curved more in one direction than in another.
Light rays have more than one focal point and focus on different
areas of the retina whereas a normal cornea is round with
even curves from side to side and top to bottom.
In the general population, most eyes have a small degree
of astigmatism and this has little effect on the vision.
If your spectacle prescription shows any number with either
a plus or a minus sign in the ‘cyl’ box you have
an astigmatic eye eg. +3.50 with regard to astigmatism ('cyl'
box) low levels are considered to be up to 1.5D whereas moderate
to high astigmatism is more than 1.6- 3.0D.
The front window of the eye is called the cornea. A normal
cornea is perfectly transparent (even more so than glass).
We see entirely through our corneas so it is not surprising
that if we have something wrong with our corneas then this
may affect our vision.
In order to see clearly, light entering the eye is focused,
first by the cornea and then by the lens of the eye. The way
light is focused depends upon the shape of the cornea and
When there is Astigmatism in the eye, this means that the
shape of part of the eye, usually the cornea, has become distorted.
If you can imagine the difference between the curves of a
football and a rugby ball, or between the shape of a tennis
ball and an egg, then that is like the difference between
corneas without or with Astigmatism.