Astigmatism is a refractive condition that occurs when the cornea (the front surface of the eye) or the lens inside the eye has mismatched curves. A normal eye has both the cornea and lens curved in a rounded shape, whereas people with astigmatism have one of these elements in an egg shape. In a perfect eye, the rounded shape of the cornea and lens refract any incoming light to produce a sharply focused image on the retina.