Blockage of which structure is known to cause glaucoma?

Glaucoma is primarily caused by an increase in intraocular pressure, which can occur when the drainage pathways for aqueous humor are obstructed. The Canal of Schlemm is a crucial structure in this drainage system. It is a small channel located in the angle of the anterior chamber of the eye that allows aqueous humor to drain from the eye into the bloodstream. When there's a blockage in the Canal of Schlemm, the aqueous humor cannot exit the eye effectively, leading to increased pressure in the eyeball, which can damage the optic nerve and ultimately result in vision loss if left untreated. This makes a blockage of the Canal of Schlemm a direct contributor to the development of glaucoma.

Other structures mentioned, while important in ocular anatomy and function, do not directly cause glaucoma through their blockage. For instance, the optic nerve is affected by increased pressure but is not the site of blockage; the ciliary body produces aqueous humor but doesn’t play a direct role in the drainage pathway; and the vitreous body, while it fills the eye and can impact intraocular pressure under certain conditions, does not specifically relate to the mechanism of glaucoma in terms of aqueous humor drainage.