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Glaucoma with normal pressure

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Q: At my last eye exam, I was told my eye pressures were normal, but later the doctor said I may be developing glaucoma. They want to schedule a bunch of tests, and I wonder if this is really necessary?

A: Medical science is constantly improving, which is good, but sometimes older ideas about a disease become less accurate, or not correct as we learn more. This has been true with Covid-19, and is true with glaucoma too. What I mean is that most people think of glaucoma as a disease causing too much pressure inside the eyes. And this can be true. However, we now know that many people, if not most, can develop glaucoma damage with eye pressures that are NOT excessively high.

I am a good example, in that when I finished my training a few decades ago, we thought most glaucoma was pressure induced. In fact, to this day most “glaucoma screenings” at health fairs only check eye pressures. But in reality, now in 2022, we know that many people...maybe most...have glaucoma damage because of inadequate blood flow to the optic nerve. We actually consider glaucoma a “vascular disease” now, more than a “pressure disease” for many patients.

Most commonly, we may find evidence in your eye exam that your optic nerves are prone to damage, or already having damage, even though your eye pressures are within normal limits. We sometimes call this “normal tension glaucoma”. To complicate this, we cannot measure your blood pressure in the back of your eyes clinically, so we have to indirectly assess the likely damage. This requires a few tests to tell us if your eyes are beginning glaucoma damage…regardless of the pressure number.

Fortunately, we have very good tests now to evaluate the optic nerve for thinning and damage. While the treatment for glaucoma is still usually an eye drop medication to be used each day, the actual type or cause of glaucoma can vary quite a bit from person to person. I should add, that two relatively common factors in this “normal pressure” glaucoma can be blood pressure that is too low, and sleep apnea. In both cases, fundamentally the optic nerve is not getting enough blood flow and oxygen to be healthy. The optic nerve begins to literally die too quickly, and left untreated, you will eventually lose your eyesight.

Lastly, my patients almost always ask if there is some lifestyle change they can make to improve this condition. Unless you have sleep apnea, or systemic hypotension ( blood pressure too low ), the answer is no. You cannot make your eye pressure higher or is very independent. Good news: glaucoma damage can be reduced or stopped with eye drop medicines or eye surgery. Glaucoma is mostly dangerous simply because it is truly pain, no pressure feeling, no blurry vision, nothing. I would advise having the tests run ( they are painless ) and follow your eye doctor’s treatment guidelines.