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What kinds of glaucoma are there?


image showing the difference between a normal eye and an eye with glaucoma

There are two major types of glaucoma.

Primary Open Angle Glaucoma

While there are many types of glaucoma, we’re going to focus on the main ones here. The most common type, primary open angle glaucoma, or POAG, is painless and often doesn’t cause vision changes (that you notice) until late in the disease. If you look at the drawing, fluid is produced next to the lens in our eye. This fluid is important, since it nourishes the eye and helps make the eye round (sort of like the water in a water balloon). The fluid then exits the eye through a drain called the trabecular meshwork. In POAG the fluid doesn’t drain very well. This causes a buildup of fluid and pressure inside the eye. This pressure is then exerted on the optic nerve (at the back of the eye) and causes damage.

Narrow Angle Glaucoma

This is exactly as it sounds. The drainage angle is narrow; this creates a choke point where the fluid can’t flow out of the eye very well. This can lead to elevated pressures and damage to the optic nerve. Rarely, the angle can become so narrow that it’s entirely closed off. This is known as acute angle-closure glaucoma. When this happens, the pressure spikes to 3-4x the normal levels and can happen within a matter of hours. The signs of an acute angle-closure attack are the following:

  • Headache
  • Vomiting
  • Sudden blurry vision
  • Severe pain
  • Rings or halos around lights

Angle closure can cause blindness if not treated appropriately and quickly.

Normal Tension Glaucoma

The last type of glaucoma that we’ll discuss is normal tension glaucoma (NTG). This is when people have normal pressures (around 10-22 mm Hg). This is a lesser understood area of glaucoma where people essentially have very sensitive optic nerves that become damaged even with normal pressures. There have been some associations with migraines and people with systemic heart diseases; however, there is still a lot we don’t know about NTG.

Some of those risk factors can only be evaluated by an Ophthalmologist, so having a routine eye exam is very important.

After assessing your risk factors your doctor will then do a dilated exam to further determine your risk for having glaucoma. Based on several different factors your doctor may choose to perform further testing such as an Optical Coherence Tomography (OCT) or a Visual Field. The OCT will measure the thickness of your optic nerve and compare your numbers with a set of control values. This will give us an idea if your nerve is thin due to the destruction of nerve tissue (which is glaucoma). The visual field will determine your level of peripheral vision. Many people who are suffering from glaucoma lose their peripheral vision and this test can detect early changes in your peripheral vision.

If you have a family history of glaucoma or have been diagnosed with glaucoma, give us a call so that we can further discuss your risk factors and develop a comprehensive treatment plan for you.