What is the name of the condition where the eye does not refract light equally in all directions?

Astigmatism is the condition where the eye does not refract light equally in all directions due to an irregular shape of the cornea or lens. In a normal eye, the cornea is evenly curved, allowing it to focus light uniformly onto the retina. However, in astigmatism, the curvature is uneven, leading to distorted or blurred vision at all distances. This uneven refractive power results in multiple focal points, causing difficulty in seeing clearly.

Other conditions listed, such as myopia (nearsightedness), hyperopia (farsightedness), and presbyopia (age-related difficulty in focusing on close objects), are related to specific focal points and distances but do not involve the irregular curvature that characterizes astigmatism. Therefore, astigmatism uniquely describes the refractive challenge caused by unequal focus in various directions.