The Eye, our organ of sight, is a nearly spherical hollow globe filled with fluids (humors). The outer layer or tunic (sclera, or white, and cornea) is fibrous and protective. The middle tunic layer (choroid, ciliary body and the iris) is vascular. The innermost layer (the retina) is nervous or sensory. The fluids in the eye are divided by the lens into the vitreous humor (behind the lens) and the aqueous humor (in front of the lens). The lens itself is flexible and suspended by ligaments which allow it to change shape to focus light on the retina, which is composed of sensory neurons

Glaucoma refers to a group of eye conditions typified by an increased fluid pressure inside the eye. The increased pressure causes compression of the optic nerve.  This nerve carries visual information from the eye to the brain, and can eventually become damaged with glaucoma.   Elevated eye pressure is the greatest risk factor for optic nerve damage in glaucoma.   If unrecognized and untreated, glaucoma can cause partial vision loss, with blindness as a possible eventual outcome