The water content in the lens is
**Core Concept**
The water content in the lens is a critical factor in maintaining its transparency and refractive power. The lens is composed of a high concentration of water, which helps to regulate its shape and focus light on the retina.
**Why the Correct Answer is Right**
The lens is composed of approximately 65-70% water, which is essential for maintaining its refractive index and transparency. The high water content in the lens helps to maintain its shape and flexibility, allowing it to change focus on objects at varying distances. The water content in the lens is regulated by the lens's epithelial cells, which produce and secrete various proteins and enzymes that help to maintain its transparency.
**Why Each Wrong Option is Incorrect**
* **Option A:** 20% - This is incorrect because the lens is composed of a much higher concentration of water than 20%.
* **Option B:** 40% - This is incorrect because while the lens is composed of a significant amount of water, 40% is still too low compared to the actual value.
* **Option C:** 80% - This is incorrect because while the lens is composed of a high concentration of water, 80% is too high compared to the actual value.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the lens's transparency is maintained by its high water content, which is regulated by the lens epithelial cells. This is a critical factor in maintaining the lens's refractive power and focus.
**Correct Answer:** C. 65-70%