**Core Concept**
The patient's symptoms suggest a problem with the ocular motor system, specifically the cranial nerves responsible for eye movements. The combination of difficulty looking downwards and laterally points towards a disorder affecting the superior oblique and lateral rectus muscles, which are innervated by cranial nerves IV and VI, respectively.

**Why the Correct Answer is Right**
The superior oblique muscle is responsible for intorsion, depression, and abduction of the eye. The lateral rectus muscle is responsible for abduction of the eye. The patient's difficulty in looking downwards and laterally suggests a weakness in these muscles. This is consistent with a cranial nerve IV palsy (trochlear nerve) or cranial nerve VI palsy (abducens nerve), which can cause difficulty in moving the eye in the downward and lateral directions. **Option A** is the correct diagnosis.

**Why Each Wrong Option is Incorrect**
**Option B:** This is not a specific diagnosis and does not explain the patient's symptoms.
**Option C:** This is a type of eye movement disorder, but it does not specifically explain the patient's difficulty in looking downwards and laterally.

**Clinical Pearl / High-Yield Fact**
A classic exam question like this one can be remembered using the "SCALP" mnemonic: Superior Oblique (IV), Cavernous Sinus, Abducens (VI), Lateral Rectus (VI), and Papilledema. This mnemonic helps to associate the cranial nerves with the relevant anatomy and clinical manifestations.

**Correct Answer:** A. **Superior Oblique Palsy**