Astigmatism is an imperfection in the curvature of the eye, more specifically, the cornea or lens. Under normal circumstances, the cornea and lens are smooth and curve equally in all directions. This helps focus light rays to the retina at the back of the eye. If the cornea or lens isn’t smooth or curves abnormally, this causes a “refractive error” in that the light rays aren’t refracted properly. This refractive error causes vision to blur for objects near and far.
There are two types of astigmatism: corneal and lenticular. Corneal astigmatism is an irregularity in the cornea, while lenticular astigmatism is an irregularity in the lens.
Astigmatism is most often treated with eyeglasses or contact lenses that correct the refractive error.
It is very common and it is estimated that there are over 3 million new cases per year in the US.