Patrick O’Neill, OD, FAAO
The reason that glaucoma is one of the leading causes of blindness is because most people don’t know they have it!
In most instances, glaucoma is a very treatable disease, but since most cases of glaucoma have no symptoms, the disease is allowed to progress unnoticed until there is advanced and permanent loss of vision.
So what exactly is glaucoma?
Glaucoma is a disease that increases pressure inside the eye. This increased pressure then pushes against and damages the optic nerve. Since the optic nerve literally connects the eye to the brain, any damage to the nerve will affect vision.
What causes glaucoma?
The exact cause of glaucoma is not known. We know a great deal about the mechanism of glaucoma, but little about why the pressure increases in the first place. Think of it this way: there are cells behind the iris that produce fluid (aqueous humor). That fluid then flows toward the front of the eye through the pupil and drains from the eye through a meshwork located where the white and iris or colored part of the eye meet. It is much like a spigot and a drain: as long as the fluid being produced equals the fluid being drained out, the pressure remains stable and normal. If the spigot is turned up, or if the drain is blocked, the pressure goes up. Most researchers feel glaucoma has to do with a blocked drain. Certain factors can put you at higher risk for glaucoma, such as:
- Advancing age
- Family history
- Long-term use of steroids (especially topical eye drops)
- Inflammation of the eye
- Advanced cataract (swelling of the lens of the eye)
- High farsightedness or nearsightedness
- Anatomically small drainage filter
How is glaucoma treated?
Let’s go back to our spigot and drain. There are two ways to lower the pressure:
- Turn down the spigot so less fluid is being produced.
- Open up the drain so more fluid can get out.
Most glaucoma is treated with eye drops that will either reduce the amount of fluid being produced, or increase the amount of fluid being drained away. That is, we either turn down the spigot, open the drain, or do both. Your eye doctor will prescribe either one drop or a combination of drops that will most effectively control your eye pressure. The goal is to reduce the pressure enough to stop damage to the optic nerve.
How long do I have to use the drops?
Think of glaucoma as you would think about high blood pressure, high cholesterol or diabetes: these are diseases that are manageable but not curable. The drops don’t make the glaucoma go away, we simply try to slow down the disease process so you can live out your normal life without losing vision. In other words, most people will use drops for the rest of their lives.
Are there ways to treat glaucoma other than eye drops?
Yes. Eye drops are the most common, but there are other methods to reduce eye pressure. Most involve improving the drainage of the eye.
- Laser surgery – An eye surgeon will use a laser to open the meshwork the fluid flows through
- Filtering surgery – An eye surgeon will fit an artificial drain (or filter) in the eye.
Why don’t I just get the surgery and not use the drops?
Surgery is usually only done if the eye drops fail to control the pressure, or if a person is unable to get drops in the eye. However, even after glaucoma surgery, you may still have to use drops.
Things to remember about glaucoma:
- Most cases of glaucoma have no symptoms. Most people will say they have glaucoma because their eye doctor told them they have glaucoma. There is no warning that a person will feel or see; the vision is usually fine, the eyes feel fine and the eyes don’t look red or irritated.
- If you’ve been told you have glaucoma, you have to trust your eye doctor and you have to believe you have glaucoma, otherwise it will be difficult for you to be compliant with your eye drops. It’s fine to get a second opinion. A good eye doctor will encourage and even help you to do so.
- You have to keep your eye appointments. You will see your eye doctor two to four times a year. Each time your pressure will be checked and specialized testing will be conducted to see if the glaucoma is stable or progressing. Remember, just checking the eye pressure does not tell you if your glaucoma is stable. The eye drops will lower your eye pressure, but the other specialized tests will tell your doctor if the pressure is low enough to stop causing damage.
- A glaucoma diagnosis is made only after carefully analyzing a series of tests, including
- Peripheral vision testing (Visual field analysis)
- Scanning the back of the eye to measure thinning of the retina (Tomography)
- Thorough analysis of the optic nerve and retinal photographs (Ophthalmoscopy)
- Measurement of the thickness of your cornea (Pachymetry)
- Careful examination of the drainage filter in the front of the eye (Gonioscopy)
- Eye pressure (Tonometry)
- A thorough and complete eye exam to rule out other problems
Myths about eye pressure:
- We used to think of eye pressure as THE glaucoma test. It’s not. It’s a piece of the glaucoma puzzle. You could have higher pressure and NOT have glaucoma, but more dangerously, you could have LOW eye pressure AND STILL HAVE GLAUCOMA!