**Core Concept**
The equatorial diameter of the lens refers to the widest dimension of the lens, measured across its equator, in the context of the human eye. This dimension is crucial for understanding the lens's shape and its role in refracting light. The equatorial diameter is one of the key parameters in ophthalmology, particularly in the assessment of lens-related disorders.

**Why the Correct Answer is Right**
The equatorial diameter of the human lens is approximately 11.5 mm. This measurement is essential in ophthalmic practice as it helps in assessing the lens's integrity and its potential impact on vision. The equatorial diameter is related to the lens's ability to accommodate and its overall shape, which can be affected by various conditions, such as cataracts or lens dislocation. The correct measurement of the equatorial diameter is critical in the diagnosis and treatment of lens-related disorders.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the equatorial diameter is not related to the axial length of the eye. While the axial length is an important parameter in ophthalmology, it is not the same as the equatorial diameter of the lens.
**Option B:** This option is incorrect because the equatorial diameter of the lens is not a measure of its curvature. The curvature of the lens is related to its ability to refract light, but it is not the same as the equatorial diameter.

**Clinical Pearl / High-Yield Fact**
The equatorial diameter of the lens is a critical parameter in ophthalmic practice, particularly in the assessment of lens-related disorders. A thorough understanding of the equatorial diameter is essential for accurate diagnosis and treatment of conditions such as cataracts or lens dislocation.

**Correct Answer:** C. 11.5 mm