What is astigmatism?

Astigmatism is a common refractive error that can occur alongside short-sightedness or long-sightedness.  In astigmatism, the cornea of the eye is not uniformly curved, but rather oval or egg-shaped. As a result, incoming light is refracted unevenly. Vision at both a distance and close up becomes distorted or blurred. The prescription for astigmatism is given as a ‘cylinder power’ (abbreviated to Cyl or Zyl) in dioptres and can be corrected using spectacles or contact lenses.