Understanding Glaucoma

Understanding Glaucoma

Glaucoma is one of the leading causes of preventable blindness in the U.S. In general, glaucoma occurs when pressure builds up in the eye and causes damage to the optic nerve. The optic nerve is like an electric cable with over a million wires that carry images from the eye to the brain. Intraocular pressure increases when the drainage area of the eye becomes clogged. This pressure elevation can occur slowly as a result of aging, or suddenly in the case of angle closure glaucoma. Glaucoma often develops over many years without causing pain or other noticeable symptoms.

Experts estimate that half of the people affected by glaucoma may not know they have it. Symptoms develop when the disease is advanced and vision loss begins to encroach on central vision. Some patients with glaucoma can even have normal or near normal eye pressures. It was once thought that high pressure within the eye was the sole cause of this optic nerve damage. Although elevated intraocular pressure is clearly a major risk factor, we now know that other factors are also involved in causing a person to develop glaucoma.

Fortunately, if it is caught early glaucoma can usually be controlled. If you are over 40, African-American, have a family history of glaucoma, are diabetic or very nearsighted, you should have your eyes checked every year.To detect glaucoma, your physician will test your visual acuity and visual field as well as the pressure in your eye.

Did You Know?

  • Glaucoma is responsible for 15 percent of blindness in adults in the United States.
  • Chronic glaucoma often causes no symptoms until late in the disease when it has already caused severe and irreversible damage to vision.
  • It is usually detected only by regular, routine eye examinations.
  • Early diagnosis and treatment can prevent visual impairment caused by glaucoma.
  • That some asthma inhalers and cortisone-containing medications can dangerously increase eye pressures.

It is worth repeating that early diagnosis and treatment are the most important factors in preventing visual impairment from glaucoma. So, don’t put off your regular, routine eye exams just because you have no symptoms especially if there is a family history of the disorder or you are taking any cortisone-containing medications

What causes glaucoma?
A clear fluid called aqueous humor circulates inside the front portion of the eye. To maintain a healthy level of pressure within the eye, a small amount of this fluid is produced constantly while an equal amount flows out of the eye through a microscopic drainage system.

Because the eye is a closed structure, if the drainage area for the aqueous humor is blocked, the excess fluid cannot flow out of the eye. Fluid pressure within the eye increases, pushing against the optic nerve and causing damage.

What are the different types of glaucoma?

  • Chronic Open-Angle Glaucoma: This is the most common form of glaucoma in the United States. The risk of developing chronic open-angle glaucoma increases with age.  The drainage angle of the eye becomes less porous over time, and pressure within the eye gradually increases, which can damage the optic nerve.  In some patients, the optic nerve becomes sensitive even to normal eye pressure and may become damaged.  Treatment is necessary to prevent further vision loss. Typically, open-angle glaucoma has no symptoms in its early stages and vision remains normal. As the optic nerve becomes more damaged, blank spots begin to appear in the field of vision. You typically won’t notice these blank spots in your day-to-day activities until the optic nerve is significantly damaged and these spots become large.
  • Closed-Angle Glaucoma: Some eyes are formed with the iris (the colored part of the eye) too close to the drainage angle. In these eyes, the iris can be sucked into the drainage angle and block it completely. Since the fluid cannot escape the eye, pressure inside the eye quickly rises causing acute angle closure glaucoma. This is an emergency situation in which the high intraocular pressure can cause permanent loss of vision in a matter of hours. Patients with acute angle closure glaucoma can have severe headaches, eye pain, nausea and vomiting.  Patients at risk for narrow angle glaucoma are usually far-sighted and have eyes that are shorter than normal. Early signs of intermittent angle closure include episodes of blurred vision, an ache over the brow region, headaches, and rainbow-colored halos around lights.  Unfortunately, two-thirds of those with closed-angle glaucoma develop it slowly without any symptoms prior to an attack.

Who is at risk for glaucoma?
Your ophthalmologist considers many kinds of information to determine your risk for developing the disease.

The most important risk factors include:

  • Age
  • Elevated eye pressure
  • Family history of glaucoma
  • African or Spanish-American ancestry
  • Far-sightedness or near-sightedness
  • Past eye injuries
  • Thinner central corneal thickness
  • Systemic health problems, including diabetes, migraine headaches, and poor circulation.

Your ophthalmologist will weigh all of these factors before deciding whether you need treatment for glaucoma, or whether you should be monitored closely as a glaucoma suspect. This means your risk of developing glaucoma is higher than normal, and you need to have regular examinations to detect the early signs of damage to the optic nerve.

How can I tell if I have glaucoma?
Unfortunately you can’t!  Most people have no symptoms when glaucoma is in its early stages. The only way to find out if you have glaucoma is to have a regular eye examination.

Why do I need an annual glaucoma check?
If you wait until your vision is impaired, glaucoma may already be quite advanced. As the optic nerve becomes more damaged, blank spots begin to appear in your field of vision. You typically won’t notice these blank spots in your day-to-day activities until the optic nerve is significantly damaged and these spots become large. Blindness results if the blank spots become large enough. With early detection and appropriate treatment, your vision can be preserved.

How is glaucoma detected?
Regular eye examinations are the best way to detect glaucoma. A glaucoma screening that checks only the pressure of the eye may miss certain types of glaucoma. The only sure way to detect glaucoma is to have a complete eye examination.

During your glaucoma evaluation, your doctor will:

  • Measure your intraocular pressure (tonometry);
  • Measure the thickness of your cornea (corneal pachymetry);
  • Inspect the drainage angle of your eye (gonioscopy);
  • Evaluate whether or not there is any optic nerve damage (ophthalmoscopy);
  • Test the peripheral vision of each eye (visual field testing, or perimetry).

Photography of the optic nerve or other computerized imaging may be recommended. Some of these tests may not be necessary for everyone. These tests may need to be repeated on a regular basis to monitor any changes in your condition.