Glaucoma

Glaucoma—The Basics

 


Glaucoma is a disease of the optic nerve, which transmits the images you see from the eye to the brain. The optic nerve is made up of many individual nerve fibers (like an electric cable with its numerous wires). Glaucoma damages nerve fibers, which can eventually cause blind spots and vision loss.

Glaucoma has to do with the pressure inside the eye, known as intraocular pressure (IOP).  The intraocular pressure is not significantly influenced by blood pressure, which is a common misperception.  When the aqueous humor (a clear liquid that normally flows in and out of the eye) cannot drain properly, pressure builds up in the eye. The resulting increase in IOP can damage the optic nerve and lead to vision loss.



Normal cup/disc ratio (<0.5)

Enlarged (glaucomatous) cup (0.8)

The most common form of glaucoma is primary open-angle glaucoma (POAG), in which the aqueous fluid is blocked from flowing out of the eye at a normal rate through the tiny drainage system (trabecular meshwork). Most people who develop primary open-angle glaucoma notice no symptoms until their vision is already impaired.

POAG:                                     

Ocular hypertension is often a forerunner to actual open-angle glaucoma. When intraocular pressure is above normal, the risk of developing glaucoma increases. Several risk factors will affect whether you will develop glaucoma, including the level of IOP, family history, and corneal thickness. If your risk is high, Dr. Haas may recommend treatment to lower your IOP to prevent future damage.

In angle-closure glaucoma, the iris (the colored part of the eye) may completely close off the drainage angle, abruptly blocking the flow of aqueous fluid and leading to a sudden increased IOP or optic nerve damage. In acute angle-closure glaucoma there is a sudden increase in IOP due to the buildup of aqueous fluid. This condition is considered an emergency because optic nerve damage and vision loss can occur within hours of the problem. Symptoms can include nausea, vomiting, seeing halos around lights, and eye pain.

Angle Closure:              

 

Even some people with “normal” IOP can experience vision loss from glaucoma. This condition is called normal-tension glaucoma. In this type of glaucoma, the optic nerve is damaged even though the IOP is considered normal. Normal-tension glaucoma is not well understood, but lowering IOP has been shown to slow progression of this form of glaucoma.

Childhood glaucoma,
which starts in infancy, childhood, or adolescence, is rare. Like primary open-angle glaucoma, there are few, if any, symptoms in the early stage. Blindness can result if it is left untreated. Like most types of glaucoma, childhood glaucoma may run in families. Signs of this disease include:

  • clouding of the cornea (the clear front part of the eye);
  • tearing; and
  • an enlarged eye.

Dr. Haas may tell you that you are at risk for glaucoma if you have one or more risk factors, including having an elevated IOP, a family history of glaucoma, certain optic nerve conditions, are of a particular ethnic background, or are of advanced age. Regular examinations are important if you are at risk for this condition.

The goal of glaucoma treatment is to lower your eye pressure to prevent or slow further vision loss. Dr. Haas will recommend treatment if the risk of vision loss is high. Treatment often consists of eyedrops but can include laser treatment or surgery to create a new drain in the eye. Glaucoma is a chronic disease that can be controlled but not cured. Ongoing monitoring (every three to six months) is needed to watch for changes. Ask us if you have any questions about glaucoma or your treatment.


Glaucoma: People of African and Hispanic Ancestry Are at Higher Risk

If you are of African or Hispanic ancestry and especially if you have a known family member with glaucoma, you are at a higher risk for vision loss from this eye disease.
Glaucoma is a disease of the optic nerve, which transmits the images you see from the eye to the brain. The optic nerve is made up of numerous nerve fibers (like an electric cable made up of many wires). Glaucoma damages nerve fibers, which can cause blind spots and loss of vision.

Glaucoma has to do with the pressure inside the eye, or intraocular pressure (IOP). When the aqueous humor (the clear liquid that normally flows in and out of the eye) cannot drain properly, pressure builds up in the eye. The resulting increase in IOP can damage the optic nerve.

Primary open-angle glaucoma
is the leading cause of blindness among people of African ancestry, occurring at a rate four times higher than among Caucasian patients. It also occurs about 10 years earlier among people of African ancestry than among Caucasians and develops more rapidly. Studies show that in the United States, African Americans between the ages of 45 and 64 are approximately 15 times more likely to go blind from glaucoma than Caucasians with glaucoma in the same age group. Primary open-angle glaucoma is also the leading cause of blindness among people of Hispanic (and especially Mexican) ancestry, occurring at a rate approaching that of people of African ancestry.

It is not clear why people of African ancestry have higher rates of glaucoma and subsequent blindness than Caucasians. One factor may be that they are more susceptible to developing elevated IOP earlier in life, which is thought to contribute to optic nerve damage and eventual vision loss. Another reason may be that they are less likely than Caucasians to have early eye examinations that might detect and treat glaucoma. This also may be a factor in the increased rate of glaucoma among Hispanics.

Glaucoma causes no symptoms early in its course; you will not experience pain or vision changes while it is developing. The best way to protect yourself and your family members against vision loss from glaucoma is by being aware of your higher risk of developing this disease and by having regular eye examinations for glaucoma at appropriate intervals.

Recommended intervals for a comprehensive eye evaluation in people of African ancestry are as follows:

  • 20 to 29 years of age: every 3 to 5 years;
  • 30 to 64 years of age: every 2 to 4 years;
  • 65 years and older: every 1 to 2 years.

It is also recommended that people of Hispanic ancestry have regular, comprehensive eye evaluations. This is especially important after age 60.
If you are diagnosed with glaucoma, please make sure to tell your family members and urge them to have an eye exam for glaucoma.

Here are some resources for more information on glaucoma:

The Glaucoma Foundation
80 Maiden Lane, Suite 1206
New York, NY 10038
Phone: 800.GLAUCOMA (452.8266)
www.glaucoma-foundation.org

The National Eye Institute
2020 Vision Place
Bethesda, MD 20892-3655
Phone: 301.496.5248
www.nei.nih.gov

Prevent Blindness America
Phone: 800.331.2020
www.preventblindness.org
The American Academy of Ophthalmology
P.O. Box 7424
San Francisco, CA 94120-7424
www.aao.org