Common Eye Conditions

Astigmatism

The power of the eye is governed to a great extent by the curve on the front of the eye called the cornea, the steeper the curve the stronger the power. Ideally we would like a spherical front curve that matched the length of the eye. In an eye that is short sighted this curve is too steep, making the power too strong. In a long-sighted eye the curve is not steep enough leaving a power that is not strong enough.

Astigmatism is normally caused by the curve being a mixture of a flatter and a steeper element. Rather than the cornea being shaped like a football with a spherical surface it is shaped more like a rugby ball with the two different curves making up the shape. The steeper curve bends the light entering the eye by one amount and the flatter curve bending it less.

The end result is that at the back of the eye there are two rather than one image produced, these do not line up with each other and a blurred image is seen. We correct this by using a lens with two powers on it, called a toric lens.