**Core Concept**
Shanti's symptoms suggest a disorder of the extraocular muscles, which are responsible for controlling eye movements. This condition is associated with a specific type of muscle weakness that affects the ability to converge and diverge the eyes, leading to diplopia (double vision).

**Why the Correct Answer is Right**
Shanti's symptoms of ptosis (drooping eyelid) and diplopia in all directions are characteristic of a condition known as Duane's retraction syndrome, a congenital disorder of the extraocular muscles. This condition is caused by an abnormal development of the lateral rectus muscle, which is responsible for outward eye movement. The resulting muscle imbalance leads to difficulty in converging and diverging the eyes, causing double vision.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to Shanti's symptoms, as it does not address the extraocular muscle weakness or the specific symptoms of ptosis and diplopia.
* **Option B:** This option may be related to eye movement disorders, but it does not specifically address the congenital nature of Duane's retraction syndrome or the characteristic symptoms of ptosis and diplopia in all directions.
* **Option C:** This option is incorrect because it does not address the specific symptoms of ptosis and diplopia in all directions, which are characteristic of Duane's retraction syndrome.

**Clinical Pearl / High-Yield Fact**
Duane's retraction syndrome is a congenital disorder that affects the extraocular muscles, leading to characteristic symptoms of ptosis and diplopia in all directions. This condition is often associated with other congenital anomalies, such as strabismus and cataracts.

**Correct Answer: C. Duane's retraction syndrome**