Glaucoma: Ask an Expert
Date: January 25, 2011
- What is considered normal eye pressure?
- Can you have glaucoma without having increased pressure inside the eye?
Katherine Jimenez: Hi, I’m Katherine Jimenez,
Sarah: And I am Sarah DiSandro. And we are with National Glaucoma Research, of the BrightFocus Foundation, a nonprofit organization leading the fight to save sight and mind.
Katherine: Today we have some glaucoma questions and answers that we would like to share with you. Our first question came in through the Ask the Expert section of our website. It was sent to us from Cindy. Her question says:
What is considered normal eye pressure?
Sarah: Thanks Cindy for sending this question to us, this really is a great question. Unfortunately, the answer is not as easy as giving you some single number. Intraocular eye pressure measures how much fluid has built up in the eye. While the "average" eye pressure is about 15, the range of "normal" eye pressure is much larger. About 9 out of 10 people will have an eye pressure reading from anywhere between 10 to 21. Even knowing this, it does not mean that if you have a pressure of 22 or higher that it’s "abnormal." Every individual and every eye is unique. There are many patients with pressures in the mid-20s who don’t have glaucoma, and they can simply be followed with routine eye exams by their eye care specialist. There are also people who’ve been diagnosed with glaucoma and even though treatment may decrease their pressure, they still experience a worsening of their glaucoma. It’s important that you see an eye care specialist so that they can do a comprehensive eye exam, and determine if your eye pressure is problematic.
Katherine: Great! Thanks Cindy for your question. Our next question comes to us from Jonathan. He asks:
Can you have glaucoma without having increased pressure inside the eye?
Sarah: Thanks Jonathan, that’s another great question. You may know that glaucoma is not just one but a group of eye disorders. In glaucoma, it’s optic nerve damage that can lead to vision loss and possibly blindness. In many people, fluid pressure increases inside the eye and damages the optic nerve. The optic nerve is a bundle of nerve fibers that carries information from the eye to the brain. Elevated eye pressure increases the risk of developing glaucoma; however, the disease can occur in people with normal or even lower than normal eye pressure. Also, people with higher than normal eye pressure don’t always develop the symptoms of glaucoma. Since normal-tension glaucoma doesn’t involve high eye pressure, it’s diagnosed by observing the optic nerve for any signs of damage. The idea here is that there is no one factor that lets a doctor know when an eye has glaucoma. The doctor will need to perform an inspection of the optic nerve initially using an ophthalmoscope, but the doctor might order more sophisticated tests, to examine the shape of the optic nerve, and other structures of the eye. In addition to the structure of the eye, the doctor will also want to examine the function of the eye. A visual field test can help determine if there is any loss of peripheral vision, or areas of vision that are developing things that we might refer to as “holes” in the person’s vision. There are a number of other tests, such as a dilated eye exam or corneal thickness measurements that might also be prescribed, and potentially repeated.
The risk factors for developing normal-tension glaucoma include a family history of glaucoma, low eye pressure, and cardiovascular disease. Ongoing research looks at all of the factors that might contribute to optic nerve damage. For example, scientists believe that optic nerves might be affected by blood flow in the eye. They’re also investigating susceptibility and genetic factors.
Katherine Jimenez: Thanks everyone for listening. Stay tuned for future podcasts on glaucoma. For more information about glaucoma or to get involved in advancing research to end this degenerative eye disease, visit brightfocus.org, or call 1-855-345-6NGR. Again, that’s 1-855-345-6647. Thank you.
Last Review: 08/30/13