During accommodation, what happens to the lens when the ciliary muscle contracts?

During accommodation, what happens to the lens when the ciliary muscle contracts?

• A. Becomes thicker and more curved.
• B. Thinner.
• C. Stays the same.
• D. Moves posteriorly.

Answer: (A)

Accommodation raises the eye’s focusing power by changing the lens shape. When the ciliary muscle contracts, it reduces the pull of the zonular fibers on the lens. With that tension released, the lens—elastic and enclosed by its capsule—rounds up and becomes thicker, especially in the central part. This increased curvature makes the lens more powerful optically, allowing you to focus on near objects. If the muscle relaxed, the zonules would pull the lens flatter, which is why the lens wouldn’t be thinner during accommodation. The lens doesn’t stay the same shape, and its primary change during accommodation is curvature and thickness, not a backward shift.

Accommodation raises the eye’s focusing power by changing the lens shape. When the ciliary muscle contracts, it reduces the pull of the zonular fibers on the lens. With that tension released, the lens—elastic and enclosed by its capsule—rounds up and becomes thicker, especially in the central part. This increased curvature makes the lens more powerful optically, allowing you to focus on near objects.

If the muscle relaxed, the zonules would pull the lens flatter, which is why the lens wouldn’t be thinner during accommodation. The lens doesn’t stay the same shape, and its primary change during accommodation is curvature and thickness, not a backward shift.