Glaucoma

Glaucoma is a condition that can result in damage to the optic nerve due to elevated intraocular pressure (IOP). This elevated pressure is a result of a build up of fluid in the eye, known as aqueous humor, because the drainage system within your eye is blocked. The drainage system or the eye is called the trabecular meshwork and is very small, only one-fiftieth of an inch. Elevated IOP for a prolonged period increases the risk of damage to the optic nerve, which leads to blindness. Once damage has occurred, there is no way of restoring the vision that has been lost. However, early detection of this eye disease can prevent further damage to occur.

Types of Glaucoma

Primary Open-Angle Glaucoma (POAG)

With this type of glaucoma, the eye’s structure is normal but there is a defect in the drainage system. There is a drainage angle between the iris and cornea where the trabecular meshwork (TM) is located; this angle is normally 45 degrees. With POAG, the angle is normal, but the cells in the TM do not function properly, not allowing the aqueous humor to drain correctly. When the fluid builds up, the IOP is raised. Normal IOP is between 10 and 21 mm Hg. Pressures 22 mm Hg and higher is considered elevated IOP. The elevated IOP gradually causes damage to the optic nerve cells. This damage is irreversible. Peripheral vision is the first to be affected, then your central vision. This is the most common type of glaucoma in the U.S.

Normal-tension Glaucoma

Damage to the optic nerve can also occur with normal IOP levels. There may not be proper blood flow to the optic nerve, which causes nerve cells to die. Normal-tension glaucoma is similar to POAG. An IOP in the normal range may still be high based on the individual because of sensitive optic nerves. In order to prevent further damage or vision loss, pressure below normal may be essential.

Angle-Closure Glaucoma

A normal drainage angle is 45 degrees. When the angle is smaller than 45 degrees, this is called angle-closure glaucoma. With the, the iris is closer to the trabecular meshwork, causing decreased flow of the fluid through the eye. The fluid is trapped behind the iris, causing elevated IOP, which in turn causes the drainage angle to become even narrower. This type of glaucoma affects half a million Americans and is prevalent among people of Asian descent.

Acute Glaucoma

Acute glaucoma is a more severe type of angle-closure glaucoma. When the pressure in the eye rises significantly, the iris is pushed against the trabecular meshwork, completely blocking the flow of fluid through the eye, causing an acute-angle glaucoma attack. This happens suddenly and is very painful causing headaches, nausea, and blurred vision. Treatment must be immediate or damage to the vision is permanent.

Pigmentary Glaucoma

Usually occurring in myopic eyes, iris pigments collect in the fluid of the eye and clog the trabecular meshwork. Because of the concavity of myopic eyes, the iris rubs against the lens and the pigment layer sheds.

There are also other types of glaucoma including secondary glaucoma, where the condition results from another eye disease, childhood glaucoma, and trauma-related glaucoma.

Causes & Risk Factors

Elevated IOP is the leading factor for glaucoma.

People at risk for developing glaucoma include:

-Family history of glaucoma

-African-American or Hispanic descent (open-angle)

-Asian descent (acute-angle)

-Over the age of 40

-Certain medical condition such as diabetes or hypertension

-Use of steroids

-Severe eye injuries

-People with severe myopia

 

People with risk factors for glaucoma should regularly get a comprehensive eye exam, at least once every one to two years. This should include eye dilation. The Eye Center of Texas does not off annual eye exams. However we are affiliated with over 300 of the best optometrists in Houston. To find an optometrist in your area, go here: OD Finder or call us at 713-797-1010.

To view diagnosis and treatment of glaucoma, click here.