In an eye with a refractive error, the mismatched curves in the eye prevent the light rays from bending properly. The result is a blurry image. There are two different types of astigmatism: corneal astigmatism, where the mismatched curves occur in the cornea, and lenticular astigmatism where the curves in the lens are mismatched. Both cause blurry vision but can occur more horizontally, vertically or diagonally.
While these are some of the main symptoms of an astigmatism, some people don’t have any symptoms at all.