**Core Concept**
Squint surgery, also known as strabismus surgery, aims to correct misalignment of the eyes by adjusting the length or position of the extraocular muscles. The optimal timing for squint surgery in newborns is crucial to ensure proper alignment and minimize the risk of complications.

**Why the Correct Answer is Right**
The correct answer is **B**. Surgery should be done between 4-6 months of age. This timing allows for the following:
- Adequate growth of the orbital bones and extraocular muscles, making the surgery more effective.
- Developmental milestones such as tracking objects and following moving toys, which help in assessing the efficacy of the surgery.
- Reduced risk of complications, including amblyopia (lazy eye), which can occur if the squint is not corrected early in life.
- Better cooperation from the child during the post-operative period, making it easier to manage any potential complications.

**Why Each Wrong Option is Incorrect**
**Option A:** Performing squint surgery in the first few weeks of life is not recommended as the orbital bones and extraocular muscles are still immature, making the surgery more challenging and increasing the risk of complications.
**Option C:** Waiting until the child is over 12 months old can lead to amblyopia, which can be challenging to treat and may result in permanent vision loss.

**Clinical Pearl / High-Yield Fact**
It's essential to note that squint surgery should only be performed by an experienced ophthalmologist or pediatric surgeon, and the decision to operate should be made on an individual basis, taking into account the child's specific needs and medical history.

**Correct Answer: B. Surgery should be done between 4-6 months of age.**