What is the function of the ciliary muscles?

Options

A. Control the shape of the lens
B. Control the amount of light
C. Help us to see in dark
D. Give colour to the eyes

Answer

### Step-by-Step Solution:

1. **Understanding Ciliary Muscles**:
- Ciliary muscles are small muscles located in the eye that play a crucial role in vision. They are attached to the lens of the eye.

2. **Role of the Lens**:
- The lens is responsible for focusing light onto the retina, which is the light-sensitive layer at the back of the eye. The lens can change its shape to adjust focus.

3. **Function of Ciliary Muscles**:
- The primary function of the ciliary muscles is to control the shape of the lens. When these muscles contract, they allow the lens to become thicker.

4. **Adjusting Focal Length**:
- When the lens becomes thicker, its focal length decreases, enabling the eye to focus on nearby objects. Conversely, when the ciliary muscles relax, the lens becomes thinner, increasing its focal length, which allows for focusing on distant objects.

5. **Application of the Concept**:
- This adjustment is essential for clear vision at varying distances. The ciliary muscles work automatically based on the distance of the object being viewed.

6. **Conclusion**:
- In summary, the ciliary muscles adjust the focal length of the lens, allowing us to see objects clearly at different distances.