Open-angle glaucoma is the most common type of glaucoma, accounting for at least 90% of all cases. In this type of glaucoma, there is a wide and open angle between the iris and cornea, and the condition develops slowly as the drainage canal ages. As the drainage canals wear out, the Aqueous fluid drains too slowly causing cloggage, which results in increased pressure inside the eye. This is a lifelong condition, occuring more often in older adults, however, younger people can also get this type of glaucoma.
In open-angle glaucoma, there is an imbalance in the production and drainage of the clear fluid that fills the anterior chamber of the eye (the space between the cornea and the iris). If vision loss occurs from primary open-angle glaucoma, it usually begins in your peripheral vision and slowly moves centrally. In some cases, too much fluid (called aqueous or aqueous humor is produced by the ciliary body inside the eye. But more often, the drainage channels (trabecular meshwork in the anterior chamber where the aqueous exits the eye become blocked. Whichever cause, the result is that the pressure inside the eye (intraocular pressure or IOP) increases — sometimes to dangerous levels. As IOP increases, the pressure pushes harder against the nerve fibers of the optic nerve, which transmits visual information to the brain. This deprives the optic nerve of oxygen and nutrients. Over time, high eye pressure can cause irreversible nerve damage and vision loss. (All About Vision, John Berdahl, MD)
Open-angle glaucoma is the most common type of glaucoma, affecting about three million Americans.