**Core Concept**
The optic nerve is responsible for transmitting visual information from the retina to the brain, and damage to this nerve can result in various visual disturbances. The optic nerve contains both afferent (sensory) and efferent (motor) fibers, including parasympathetic fibers that regulate pupil constriction.

**Why the Correct Answer is Right**
Optic nerve damage can lead to visual field defects, blindness, or even pain due to the involvement of afferent fibers. The parasympathetic fibers within the optic nerve regulate pupil constriction via the Edinger-Westphal nucleus, which controls the sphincter pupillae muscle. Damage to these fibers can result in a dilated pupil (mydriasis) on the same side as the injury.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided, but if it were a potential consequence of optic nerve injury, it would be incorrect if it did not involve visual disturbances or pupil changes.

**Option B:** A decrease in visual acuity is a possible consequence of optic nerve injury, as it can result in blindness or significant visual impairment.

**Option C:** An increase in intraocular pressure (IOP) is not a direct consequence of optic nerve injury, although it can be a secondary effect of certain conditions that damage the optic nerve, such as glaucoma.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that optic nerve damage can result in pain due to the involvement of afferent fibers, a phenomenon known as retrobulbar neuralgia.

**Correct Answer:** C. An increase in intraocular pressure (IOP) is not a direct consequence of optic nerve injury.