What optical condition results from unequal curvatures of the cornea or lens causing different focal lengths in different meridians?

What optical condition results from unequal curvatures of the cornea or lens causing different focal lengths in different meridians?

• A. Myopia.
• B. Hyperopia.
• C. Astigmatism.
• D. Presbyopia.

Answer: (C)

Astigmatism happens when the cornea or lens isn’t equally curved in all directions, so light is focused at different distances along different meridians. Instead of a single sharp focus on the retina, you get multiple focal points (or a stretched focus), leading to blurred or distorted vision. The uneven curvature is often described as toricity, with two principal meridians at different powers. This contrasts with myopia or hyperopia, where the entire eye’s focal point is too close or too far from the retina, and with presbyopia, which is an age-related loss of accommodation.

Astigmatism happens when the cornea or lens isn’t equally curved in all directions, so light is focused at different distances along different meridians. Instead of a single sharp focus on the retina, you get multiple focal points (or a stretched focus), leading to blurred or distorted vision. The uneven curvature is often described as toricity, with two principal meridians at different powers. This contrasts with myopia or hyperopia, where the entire eye’s focal point is too close or too far from the retina, and with presbyopia, which is an age-related loss of accommodation.