Which refractive error causes different focal lengths in different planes on the cornea, resulting in blurred vision at distance and at near?

Astigmatism is characterized by an irregular curvature of the cornea or lens, which causes light entering the eye to be focused unevenly. This means that there are multiple focal points instead of a single point. As a result, images can appear blurry for both near and distant vision. The different focal lengths are due to the varying degrees of curvature in different meridians of the cornea. This leads to challenges in seeing clearly at all distances, making it essential for individuals with astigmatism to have corrective lenses tailored to address these disparities in focal points.

In contrast, presbyopia is age-related and primarily affects near vision as the lens becomes less flexible, while myopia (nearsightedness) is when distant objects appear blurry but near objects are clear. Hyperopia (farsightedness) allows for clear vision at a distance but can cause nearby objects to be blurry, especially if the eye cannot accommodate. Astigmatism is specifically different as it affects both near and distance vision due to its complex refractive nature.