Certified Paraoptometric (CPO) Practice Exam 2025

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What role does the ciliary muscle play in vision?

  1. Helps maintain the shape of the eyeball

  2. Controls eye movement

  3. Alters the shape of the crystalline lens

  4. Regulates light entering the eye

The correct answer is: Alters the shape of the crystalline lens

The ciliary muscle plays a crucial role in altering the shape of the crystalline lens, which is essential for focusing light onto the retina. When the ciliary muscle contracts, it causes the tension in the zonular fibers to decrease, allowing the lens to become thicker and more curved. This increased curvature is necessary for focusing on near objects, a process known as accommodation. Conversely, when the ciliary muscle relaxes, the lens flattens for distance vision. This ability to change shape enables clear vision at various distances, making the ciliary muscle integral to our visual acuity.

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