Which of the following is correct for lens focusing, while seeing distant object ?

Options

A. Tight suspensory ligaments and rounded lens
B. Contracted ciliary muscles and rounded lens
C. Relaxed ciliary muscles and tight suspensory ligament
D. Contracted ciliary muscles and relaxed suspensory ligaments

Answer

To determine the correct option for lens focusing while seeing a distant object, we need to understand how the eye adjusts to focus on objects at different distances. Here’s a step-by-step breakdown of the process:

### Step-by-Step Solution:

1. **Understanding Eye Anatomy**: The eye contains ciliary muscles and suspensory ligaments that play a crucial role in adjusting the shape of the lens. The lens changes its shape to focus light on the retina.

2. **Focusing on Distant Objects**: When focusing on distant objects, the eye needs to flatten the lens to reduce its curvature. This is necessary because light rays from distant objects are nearly parallel when they enter the eye.

3. **Ciliary Muscles and Suspensory Ligaments**:
- **Ciliary Muscles**: When the ciliary muscles are relaxed, they do not exert tension on the lens.
- **Suspensory Ligaments**: When the ciliary muscles are relaxed, the suspensory ligaments become tight, pulling on the lens and causing it to flatten.

4. **Evaluating the Options**:
- **Option 1**: Tight suspensory ligament and rounded lens - Incorrect, as the lens should be flattened for distant vision.
- **Option 2**: Contract ciliary muscles and rounded lens - Incorrect, as contracting ciliary muscles would cause the lens to become rounded, which is for near vision.
- **Option 3**: Relaxed ciliary muscles and tight suspensory ligament - Correct, as this configuration allows the lens to flatten for distant vision.
- **Option 4**: Contract ciliary muscles and relax suspensory ligament - Incorrect, as this would make the lens rounded for near vision.

5. **Conclusion**: The correct answer is **Option 3**: relaxed ciliary muscles and tight suspensory ligament.