Astigmatism is a common form of visual impairment in which part of an image is blurred, due to an irregularity in the curvature of the front surface of the eye, the cornea. In “regular astigmatism” the curve of the cornea is shaped more like a spoon than a sphere. Light rays entering the eye are not uniformly focused on the retina. In “irregular astigmatism” the cornea is shaped like a spoon or a sphere but with various distortions or dents in the surface. Regular astigmatism is usually easily corrected, but irregular astigmatism may require corneal transplant. The most common cause of irregular astigmatism is keratoconus and it often persists even after corneal transplant.