In an ideal world, the surface of the cornea (the transparent layer of tissue at the front of the eye) would be perfectly spherical in shape, and incoming light would form a single focus, ideally on the retina at the back of the eye.
However, in the real world the cornea is often irregular in shape – its front surface more closely resembling the shape of a rugby ball than a football. That’s to say it can be a little longer and flatter in one direction than the other. This causes the light to form two different focal points within the eye – and this is known as astigmatism.
Astigmatism is common amongst both long-sighted and short-sighted people. Vision without glasses can be blurred and slightly distorted at all distances.
Everyone’s vision changes over time and you may experience one or more of the above conditions. That is why it is important to have regular eye examinations.
All images on this page have been supplied courtesy of Hoya Lens UK.