This pressure is called IOP, or intraocular pressure. After nourishing the cornea and lens, the fluid flows out through a very tiny spongy tissue called the trabecular meshwork, which serves as the drain of the eye. When this drain becomes clogged, fluid cannot leave the eye as fast as it is produced, causing the fluid to back up, which in turn causes increased pressure to build up within the eye. When the pressure in the eye builds, the nerve cells that make up the optic nerve and their blood supply become compressed, causing them to become damaged and, eventually, die. The death of these cells results in permanent visual loss, but early diagnosis and treatment of glaucoma can prevent this from happening.
Acute glaucoma develops suddenly, leading to a rapid loss of vision and severe pain in the eye.
Chronic glaucoma develops slowly and painlessly over many years and there may be no noticeable symptoms until the eyes are badly damaged. Congenital glaucoma is due to a defect in the drainage apparatus of the eye. It is normally present from birth and can lead to blindness. Secondary glaucoma occurs due to an underlying disorder such as uveitis or from usage of certain drugs such as corticoseroid eyedrops. The only way to detect glaucoma is to have your eyes checked regularly by an eye care professional.