What condition is characterized by irregular curvature of the cornea?

Astigmatism is a refractive error caused by an irregular curvature of the cornea or sometimes the lens of the eye. In a healthy eye, the cornea has a smooth, spherical shape, allowing light to focus evenly on the retina. However, in astigmatism, the cornea is shaped more like a football, which leads to multiple focal points instead of a single point of focus. This irregular shape can cause blurred or distorted vision at various distances. Hence, astigmatism is directly linked to the irregular curvature of the cornea.

The other conditions listed—cataract, myopia, and hyperopia—are not primarily associated with the curvature of the cornea. Cataracts involve the clouding of the lens, myopia is caused by the eyeball being too long or the cornea being too steeply curved, and hyperopia often occurs when the eyeball is too short or the cornea is too flat. These conditions relate to how light focuses in the eye, but they do not specifically involve the irregular curvature of the cornea like astigmatism does.