**Core Concept**
Uncrossed diplopia, also known as esotropic deviation, occurs when the images seen by each eye are not aligned, resulting in double vision that is not symmetrical. This condition is often associated with disorders of the extraocular muscles or cranial nerves controlling eye movement.

**Why the Correct Answer is Right**
Uncrossed diplopia is typically seen in conditions where there is a restriction of adduction, such as in Duane's retraction syndrome or in cases of medial rectus palsy. This is because the medial rectus muscle is primarily responsible for adduction, and its weakness or paralysis leads to a lack of convergence, resulting in esotropic deviation. The brain then attempts to compensate by increasing the action of the lateral rectus muscle, which can lead to overaction of this muscle and further exacerbate the deviation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a condition that typically results in uncrossed diplopia.
**Option B:** This option is incorrect because it refers to crossed diplopia, which is a different condition characterized by a horizontal deviation of the visual axis.
**Option C:** This option is incorrect because it does not accurately describe a condition that is associated with uncrossed diplopia.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that uncrossed diplopia is often associated with disorders of the medial rectus muscle, which is responsible for adduction. This can help you to quickly identify the underlying cause of esotropic deviation in patients presenting with this symptom.

**Correct Answer: D. Medial rectus palsy.