Which structure in the eye adjusts focus by changing its shape?

Which structure in the eye adjusts focus by changing its shape?

• A. Retina
• B. Lens (via the ciliary body and zonular fibers)
• C. Iris
• D. Cornea

Answer: (B)

Focusing at different distances is done through accommodation, which changes the lens’s shape to adjust the eye’s focal length. The lens is the structure that changes its curvature, controlled by the ciliary body and the zonular fibers attached to the lens capsule. When you look at something up close, the ciliary muscle contracts, the ciliary body moves inward, and the zonular fibers relax. This allows the lens to become thicker and more curved, increasing its refractive power so the image lands on the retina. For distant vision, the ciliary muscle relaxes, the zonular fibers pull the lens flatter, reducing its power. The retina, iris, and cornea have important roles in vision, but the lens is the adjustable element that changes shape to focus.

Focusing at different distances is done through accommodation, which changes the lens’s shape to adjust the eye’s focal length. The lens is the structure that changes its curvature, controlled by the ciliary body and the zonular fibers attached to the lens capsule. When you look at something up close, the ciliary muscle contracts, the ciliary body moves inward, and the zonular fibers relax. This allows the lens to become thicker and more curved, increasing its refractive power so the image lands on the retina. For distant vision, the ciliary muscle relaxes, the zonular fibers pull the lens flatter, reducing its power. The retina, iris, and cornea have important roles in vision, but the lens is the adjustable element that changes shape to focus.