Astigmatism is caused by defective curvature of which structures?

Astigmatism is caused by defective curvature of which structures?

• A. Iris
• B. Pupil
• C. Cornea or lens
• D. Retina

Answer: (C)

Astigmatism happens when the eye’s curved refractive surfaces aren’t the same in all directions, so light rays don’t come to a single focus on the retina. The front surface, the cornea, normally has a roughly uniform curvature, but if it’s steeper in one meridian than another, or if the lens inside the eye has irregular curvature, each meridian focuses light at a different distance. That mismatch creates blurred or distorted vision because there isn’t one clean focal point. The iris and pupil control how much light enters but don’t determine how light is bent, and the retina is the light-sensitive layer where the image lands after focusing. So the defect lies in the curvature of the cornea or the lens, making those structures responsible for astigmatism.

Astigmatism happens when the eye’s curved refractive surfaces aren’t the same in all directions, so light rays don’t come to a single focus on the retina. The front surface, the cornea, normally has a roughly uniform curvature, but if it’s steeper in one meridian than another, or if the lens inside the eye has irregular curvature, each meridian focuses light at a different distance. That mismatch creates blurred or distorted vision because there isn’t one clean focal point.

The iris and pupil control how much light enters but don’t determine how light is bent, and the retina is the light-sensitive layer where the image lands after focusing. So the defect lies in the curvature of the cornea or the lens, making those structures responsible for astigmatism.