Astigmatism is a vision condition caused by the cornea or lens having an irregular curvature, resulting in blurred vision. It occurs when the eye's optical system causes light rays to focus in lines rather than points on the retina. Astigmatism can be regular, meaning the refractive power changes uniformly between meridians, or irregular. Regular astigmatism is further classified as simple, compound, or mixed depending on where the focal lines fall in relation to the retina. Symptoms include blurry or distorted vision. Astigmatism is diagnosed via eye exams and treated with corrective lenses, contact lenses, or refractive surgery.