What is the role of the ciliary body in lens accommodation?

What is the role of the ciliary body in lens accommodation?

• A. It secretes tears.
• B. It contracts to change the lens curvature for focusing on near or far objects.
• C. It modulates pupil size.
• D. It transduces light.

Answer: (B)

Accommodation depends on changing the lens shape through the actions of the ciliary body. The ciliary muscle forms a circular band around the lens; when it contracts, it reduces the tension of the zonular fibers attached to the lens. With less tension, the lens becomes more curved, increasing its refractive power for near objects. When the muscle relaxes, the zonules pull on the lens and flatten it for distance vision. This process is driven mainly by parasympathetic input causing ciliary muscle contraction. Other roles listed—secreting tears, adjusting pupil size, or transducing light—are handled by different ocular structures (lacrimal glands, iris muscles, and retina, respectively).

Accommodation depends on changing the lens shape through the actions of the ciliary body. The ciliary muscle forms a circular band around the lens; when it contracts, it reduces the tension of the zonular fibers attached to the lens. With less tension, the lens becomes more curved, increasing its refractive power for near objects. When the muscle relaxes, the zonules pull on the lens and flatten it for distance vision. This process is driven mainly by parasympathetic input causing ciliary muscle contraction. Other roles listed—secreting tears, adjusting pupil size, or transducing light—are handled by different ocular structures (lacrimal glands, iris muscles, and retina, respectively).