**Core Concept**
Intraocular pressure (IOP) is a critical parameter in ophthalmology, reflecting the balance between the production and drainage of aqueous humor in the eye. The normal range of IOP is between 10-21 mmHg, and elevated IOP is a major risk factor for glaucoma.

**Why the Correct Answer is Right**
The correct answer is related to the regulation of IOP. The trabecular meshwork is a critical structure responsible for the drainage of aqueous humor from the eye, and its dysfunction can lead to elevated IOP. The uveoscleral pathway is another route for aqueous humor drainage, but it plays a relatively minor role in IOP regulation. The ciliary body produces aqueous humor, which enters the anterior chamber and increases IOP.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the optic nerve head is the site of damage in glaucoma, not the primary regulator of IOP.
**Option B:** This option is incorrect because the ciliary body is responsible for producing aqueous humor, not regulating its drainage.
**Option C:** This option is incorrect because the uveoscleral pathway is a secondary route for aqueous humor drainage and plays a minor role in IOP regulation.

**Clinical Pearl / High-Yield Fact**
The Goldman applanation tonometer is a common device used to measure IOP, but its accuracy can be affected by changes in corneal thickness. A thorough understanding of IOP regulation and measurement is essential for diagnosing and managing glaucoma.

**Correct Answer: B** Elevated intraocular pressure is primarily regulated by the trabecular meshwork.