There are several types of glaucoma:

Primary Open Angle Glaucoma
Normal Pressure Glaucoma
Acute Angle Closure Glaucoma
Chronic Angle Closure Glaucoma
Plateau Iris Syndrome
Secondary Glaucoma
Congenital Glaucoma

Lay definitions of glaucoma terms:

Aqueous Humour - The fluid contained within the front part of the eye.

Bleb - A "blister" or cyst that forms under the eyelid after glaucoma surgery

Ciliary Body- The part of the eye behind the iris that produces fluid in the eye

Conjunctiva - A thin, transparent membrane that lines the front of the eyeball, except for the cornea.

Cornea - The clear part of the eye located in front of the iris. Part of the eye’s protective covering.

Drainage Canals - Small openings around the outer edge of the iris, which provide the final pathway for fluid to leave the inside of the eye.  Sometimes referred to as the trabecular meshwork or, Schlemm’s canal.

5-FU - A medication that stops the healing process. Sometimes used around the new drainage hole created during surgery (the bleb) to stop it from healing or scarring over.

Glaucoma Suspect - A person may be considered a glaucoma suspect on the basis of high intraocular pressure, a suspicious appearance of the optic disc or visual field, a family history of glaucoma, or narrow angles between the iris and cornea.

Gonioscopy - In this test, a contact lens that contains a mirror is gently placed on the eye. The mirror lets the doctor look sideways into the eye to check whether the angle where the iris meets the cornea is open or closed. This helps the doctor decide whether open-angle or angle-closure glaucoma is present.

Intraocular Pressure (IOP) - The internal pressure of the eye. Normal intraocular pressure usually ranges from 10-22 mm Hg, although people with relatively low pressures can still have glaucoma (see normal tension glaucoma.)

Iris - The colored part of the eye that can expand or contract to allow just the right amount of light to enter the eye.

Laser Surgery - A type of surgery in which a tiny, powerful beam of light is used to solve problems in the eye. There are three common forms of laser surgery for glaucoma:
(1) Laser Peripheral Iridotomy - Creates a new drainage hole in the iris, allowing the iris to fall away from the outflow channel so fluid can drain out of the eye more effectively
(2) Selective Laser Trabeculoplasty - In this procedure, the laser is aimed toward the normal drainage channels of the eye, so as to open those channels so fluid can leave the eye more efficiently.
(3) Laser Cyclophotocoagulation - This laser procedure is usually used in people who have severe glaucoma and are not responsive to standard glaucoma surgery.

Lens - Located behind the iris, it helps to focus light onto the retina. The lens grows throughout life, and can be a cause of glaucoma. Also, cataract surgery to remove the lens can often help to lower eye pressure.

mm Hg - An abbreviation for “millimetres of mercury,” the scale for recording intraocular pressure.

Normal Pressure Glaucoma or Normal Tension Glaucoma - A relatively common form of glaucoma in which intraocular pressure stays within the normal range (10-22 mm Hg), but damage still occurs to the optic nerve and visual fields.

Optic Nerve - The nerve in the back of the eye that carries visual signals to the brain.

Perimetry - (Also known as the visual field test.) A test that produces a map of the complete field of vision, designed to determine whether there is damage to any area of vision.

Peripheral Vision - The top, sides, and bottom areas of vision, which are in most cases the first parts of vision affected by glaucoma.

Pupil - The opening that controls how much light enters the inner part of the eye.

Retina - The inner lining of the back of the eye, that transmits light signals to the brain down the optic nerve.

Sclera - The tough, white, protective, outer coat of the eye.

Tonometry - The use of a device to measure the pressure within the eye.

Trabecular Meshwork - The name of the mesh-like drainage canals in the front of the eye. This is the part of the eye that is treated in SLT laser treatment.