Which structure controls accommodation by changing optical power to maintain a clear image?

• A. Ciliary Body
• B. Sclera
• C. Cornea
• D. Lens

Answer: (A)

Accommodation is the eye’s way of changing its optical power to keep a image sharp at different distances, and the ciliary body is what drives that change. The ciliary muscle—part of the ciliary body—contracts to reduce tension on the zonular fibers attached to the lens. That release lets the lens become thicker and more curved, increasing its refractive power for near objects. When you shift to viewing distant objects, the muscle relaxes, the zonules tighten, and the lens flattens to decrease power. The sclera doesn’t adjust focusing; the cornea provides most of the eye’s fixed refractive power and doesn’t change shape for accommodation. The lens itself is the light-bending element that changes shape, but the control signal and mechanism come from the ciliary body.