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Acute Angle Closure
- Acute Glaucoma
In acute glaucoma, the aqueous fluid behind the iris does not flow properly into the anterior chamber, and causes the iris to be pushed forward toward the angle, thereby obstructing it. IOP increases suddenly, and this sudden rise in pressure can occur within a matter of hours and become very painful.
- Angle-closure Glaucoma
A form of glaucoma where the anterior chamber tends to be smaller than average. Aqueous fluid is prevented from exiting the eye by a blockage of the drain. When the angle is completely blocked, the IOP is elevated which may lead to glaucoma.
Anterior Chamber
The space in front of the iris and behind the cornea.
Ciliary Body
Tissues located around the lens of your eye that produce the aqueous fluid that nourishes the eye.
Congenital Glaucoma
A rare form of glaucoma that occurs in babies and young children. This condition can be inherited. It is usually the result of incorrect or incomplete development of the eye’s drainage canals during the prenatal period.
Cup
A funnel shaped depression at or near the center of the optic disc through which pass the central retinal vessels.
Cup-to-disc Ratio
The ratio of horizontal and vertical diameter of the rims of the physiological cup to that of the horizontal and vertical diameter of the optic disc. It is usually less than 0.5. If there is a difference in ratio between the two eyes, or if there is progressive enlargement of the cup, glaucoma may be suspected.
Drainage Canals (Trabecular Meshwork)
Small openings around the outer edge of your iris. These canals provide the final pathway for fluid to leave the inside of the eye. (Usually referred to as the trabecular meshwork or Schlemm’s canal.)
Glaucoma
Glaucoma is the name given to a group of eye diseases that damage the optic nerve and can result in serious vision loss over time. In many, but not all patients it is caused by increased pressure within the eye.
Glaucoma Suspect
A person whose ocular signs show they may have glaucoma or may develop glaucoma in the future. This term includes patients with ocular hypertension (persons with elevated intraocular pressure but no detectable optic nerve or visual field damage), and patients whose optic disc or visual field appearance is suspicious.
Gonioscopy
A diagnostic test in which a lens that contains a mirror is gently placed on the eye. The mirror lets the eye specialist look sideways into the eye to check whether the angle where your iris meets the cornea is open or closed. This helps the eye specialist determine whether open-angle or angle-closure glaucoma is present.
Intraocular Pressure (IOP)
The measure of fluid pressure inside your eye. The most significant risk factor for glaucoma is elevated IOP. Statistically normal intraocular pressure usually ranges from 12–21 mm Hg, although people with relatively low pressure can still have glaucoma (see normal tension glaucoma) and people with high pressure can still have healthy eyes.
Laser Iridotomy
The use of a special laser to produce a small hole in the iris. This removes the obstruction (pupil block) to aqueous flow from the posterior to the anterior chamber and the risk of angle closure.
mm Hg
An abbreviation for ‘millimeters of mercury,’ which is a scale for recording intraocular pressure.
Normal Tension Glaucoma
Also known as low tension glaucoma. Characterized by progressive optic nerve damage and visual field loss with a statistically normal intraocular pressure. Often patients with glaucoma have eye pressures that fall within the usual range, but even for these patients, reduction of eye pressures helps to slow progression of the disease. It may be related to poor blood flow to the optic nerve or other factors which lead to death of the cells.
Ocular Hypertension
The condition when a person has elevated eye pressure but no detectable optic nerve or visual field damage. The term is used to distinguish people with elevated eye pressure from those with glaucomatous injury to the optic nerve. While not all people with ocular hypertension develop glaucoma, there is an increased risk of glaucoma among those with ocular hypertension.
Open-angle Glaucoma
This is the most common type of glaucoma. Normally associated with increased intraocular pressure, which can lead to visual field loss and optic nerve damage. There is no visible abnormality with the trabecular meshwork; however, the aqueous fluid is unable to flow correctly.
Ophthalmoscopy
An exam where your eye specialist uses an instrument called an ophthalmoscope to look directly through the pupil of your eye at the optic nerve. The color and appearance of the optic nerve can indicate whether or not damage from glaucoma is present and how extensive it is.
Optic Disc
Region of the fundus of the eye corresponding to the optic nerve head.
Optic Nerve
The bundle of nerve fibers that carry visual messages from your retina to your brain.
Optic Neuropathy
A diseased optic nerve; this disease can come from many conditions. It is not a finite disease.
Perimetry
A diagnostic exam also known as the visual field test which measures the degree of damage to your vision. In glaucoma management, each eye is tested separately.
Pigmentary Glaucoma
A type of open-angle glaucoma where the pigment layer of the iris rubs onto the lens causing iris pigment particles to shed and plug the pores of the trabecular meshwork, thereby increasing intraocular pressure.
Retina
The part of the eye that converts images from your eye’s optical system into electrical impulses which are sent to the brain through the optic nerve.
Retinal Ganglion Cells (RGCs)
The innermost layer of cells that line the retina at the back of the eye. RGCs are nerve cells which transmit visual information from the eye to the brain and are destroyed in glaucoma.
Tonometry
The use of a tonometer to measure the fluid pressure in your eye.
Trabeculectomy
A form of traditional surgery where the surgeon removes a small section of the trabecular meshwork (the eye’s drain). This allows aqueous humor to bypass the blocked trabecular meshwork to drain more easily.
Trabeculoplasty
The most common form of laser surgery performed for open-angle glaucoma. This procedure takes between 10–20 minutes, is painless, and can be performed in either an eye specialist's office or an outpatient facility.
Trauma-related Glaucoma
A blow to the eye, chemical burn, or penetrating injury may lead to the development of glaucoma, in either acute or chronic forms. This can be due to a mechanism disruption or physical change within the eye’s drainage system.
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