**Core Concept**
Retrobulbar injection of xylocaine (lidocaine) is a regional anesthetic technique used to provide local anesthesia for ophthalmic procedures. This technique involves injecting a local anesthetic into the retrobulbar space, which surrounds the eyeball, to block the transmission of nerve impulses.

**Why the Correct Answer is Right**
The retrobulbar space contains the optic nerve, which is the primary target for the anesthetic effect. The optic nerve is surrounded by the sheaths of the optic nerve, including the dura mater, arachnoid mater, and pia mater. The anesthetic agent, xylocaine, diffuses through these sheaths and blocks the action potential in the optic nerve, preventing pain transmission. Additionally, the retrobulbar space also contains the oculomotor nerve, the trochlear nerve, and the abducens nerve, which are responsible for eye movement. The anesthetic agent can also block these nerves, contributing to the blockade of eye movements.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the optic nerve is indeed blocked by retrobulbar injection of xylocaine.

**Option B:** This option is incorrect because the oculomotor nerve, which is responsible for eye movement, is also blocked by retrobulbar injection of xylocaine.

**Option C:** This option is incorrect because the trochlear nerve, which is also responsible for eye movement, is also blocked by retrobulbar injection of xylocaine.

**Clinical Pearl / High-Yield Fact**
One of the key considerations when performing a retrobulbar injection is to avoid injecting the anesthetic agent into the globe of the eye, as this can cause serious complications, including retinal detachment and optic nerve damage.

**Correct Answer: D**