Astigmatism
The light rays are being focused onto the retina, the result is clear vision in all ranges.
Astigmatism is caused by the fact that the eye’s surface, the cornea, isn’t spherical.
Astigmatism is a condition that causes blur and discomfort at all distances. Stigma is the Greek word for point. When an “A” is placed in front it, it means not. So Astigmatism is condition in which the light reaching the retina does not focus equally at one plane or point. It’s caused by the fact that the eye’s surface, the cornea, isn’t spherical. Imagine the surface of a football. Along it’s long meridian, it has a radius of curvature that is longer than the radius 90 degrees away from it. If you now imagine that this surface is transparent, as the cornea is, the light moving through it will be affected differently according to which meridian is passes through.
Astigmatism is compensated with lenses that are specially ground to offset the focusing error and bring all the light to focus in the same plane. It can be compensated with contact lenses also, and in some cases is susceptible to surgical correction in an adult cornea.