**Core Concept**
The Helmholtz theory of accommodation explains the mechanism of focusing on near objects by the crystalline lens in the eye. It involves the change in the lens's refractive power to converge light rays on the retina.

**Why the Correct Answer is Right**
According to the Helmholtz theory, accommodation occurs due to the contraction of the ciliary muscles, which releases the tension on the zonular fibers attached to the lens. This results in the lens becoming more spherical, increasing its refractive power and allowing it to focus on near objects. The lens's ability to change shape is made possible by the elastic properties of the lens capsule and the lens fibers themselves.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the mechanism of accommodation as proposed by the Helmholtz theory.
**Option B:** This option is incorrect because it incorrectly identifies the structure responsible for changing the lens's refractive power.
**Option C:** This option is incorrect because it does not accurately describe the role of the ciliary muscles in the Helmholtz theory of accommodation.

**Clinical Pearl / High-Yield Fact**
The Helmholtz theory of accommodation highlights the importance of the ciliary muscles and the zonular fibers in regulating the lens's refractive power. This mechanism is essential for near vision and is often compromised in conditions such as presbyopia.

**Correct Answer: C. The ciliary muscles contract to release tension on the zonular fibers, allowing the lens to become more spherical and increase its refractive power for near vision.**