Mydriasis is :-

Options

A. Contraction in suspensory ligament
B. Decrease diameter of pupil, due to contraction in radial dilatory muscles
C. Increase diameter of pupil, due to contraction in circular sphincter muscle
D. Increase diameter of pupil, due to contraction in radial dilatory muscles

Answer

**Step-by-Step Solution:**

1. **Understanding Mydriasis**: Mydriasis refers to the condition of having an enlarged pupil. It is important to differentiate it from miosis, which is the constriction of the pupil.

2. **Identifying the Options**: The question provides four options regarding what mydriasis is:
- A. Contraction in suspensory ligament
- B. Decreased diameter of pupil due to contraction in radial dilatory muscles
- C. Increased diameter of pupil due to contraction in circumspective muscles
- D. Increased diameter of pupil due to contraction in radial dilatory muscles

3. **Analyzing the Options**:
- **Option A**: Contraction in the suspensory ligament is not related to pupil size; it pertains to the lens.
- **Option B**: This describes miosis, not mydriasis, as it mentions a decrease in pupil size.
- **Option C**: This option incorrectly states that mydriasis is due to contraction in circumspective (circular) muscles, which would lead to pupil constriction.
- **Option D**: This correctly states that mydriasis is the increased diameter of the pupil due to contraction in radial dilatory muscles.

4. **Conclusion**: The correct answer is **D. Increased diameter of pupil due to contraction in radial dilatory muscles**. This is because during mydriasis, the radial muscles contract, leading to an enlargement of the pupil.