What is the primary cause of glaucoma?

The primary cause of glaucoma is fluid buildup in the eye. This buildup occurs when the aqueous humor, the fluid that helps maintain intraocular pressure, does not drain properly. When the fluid cannot exit the eye effectively, it leads to increased intraocular pressure. Over time, this pressure can damage the optic nerve, which is crucial for vision. If left untreated, glaucoma can result in vision loss or even blindness.

The other options relate to different eye conditions or phenomena. For example, a cloudy lens usually describes cataracts, where the lens becomes opaque and affects vision but is not related to the pressure dynamics that cause glaucoma. Inflammation of the retina, known as retinitis, involves different symptoms and does not directly pertain to the intraocular pressure associated with glaucoma. Lastly, increased pressure in the brain can lead to a condition known as intracranial hypertension, but this is distinct from the mechanisms of glaucoma, which is specifically related to the pressure within the eye itself. Understanding the specific cause of glaucoma is crucial for effective prevention and treatment.