Astigmatism is diagnosed in the course of a comprehensive eye examination. If the degree of astigmatism is minimal and there is no myopia or hyperopia present, then corrective lenses may not be needed. If the degree of astigmatism is significant enough to cause eyestrain, headache or distortion in vision then prescriptive lenses should be used to obtain clear and comfortable vision.
Your eye care professional will recommend the appropriate corrective eyewear, suitable for patient needs so vision can be restored. Since the cornea is shaped as a football in these patients, the lenses needed would have to correct the shape in two opposite meridians. Therefore, cylindrical or toric lenses are needed for this purpose.
Astigmatism usually occurs when the cornea has an irregular curvature instead of a spherical shape. Normally the cornea is smooth and equally curved so that light entering through the cornea can be focused equally on all planes onto the macula. Instead the cornea is curved more in one direction than in the other, just like an oval or football. Therefore, light rays will be focused at different locations in the eye. Astigmatism can be caused by eye injuries or surgeries that induce scarring or from corneal diseases such as keratoconus. The exact reason for differences in corneal shape remains unknown, but usually astigmatism is inherited by nature. This is why more people are prone to develop astigmatism than others.