In this EyeFAQ roundup presented by Glaucoma Research Foundation, leading ophthalmologists answer questions from patients about traumatic glaucoma, natural childbirth and glaucoma, how vision loss is defined and measured, and why it’s important to have so many glaucoma examinations.
These videos from January 2021 include information and tips from Andrew Iwach, MD of the Glaucoma Center of San Francisco, Davinder Grover, MD, MPH from the Glaucoma Associates of Texas, and Ranya G. Habash, MD from the Bascom Palmer Eye Institute.
Q: Can a Traumatic Head Injury Cause Glaucoma?
Ranya G. Habash, MD: Head injuries can cause glaucoma because there’s a traumatic component. That trauma, especially if you have direct eye trauma can cause things like inflammation and damage to the structures of the eye that drain the [fluids to maintain the] pressure appropriately.
Just imagine if the drain in your sink gets clogged or something is covering it, or something breaks, then it can’t filter the water as well. This is the same kind of thing that happens in the eye too. The structures in there that are supposed to keep the pressure regulated can’t act the same way that they need to because sometimes there’s scar tissue or damage to those filtering structures.
Sometimes we see it in athletes, for instance, who get hit in the eye or a basketball injury to the eye. We see it in people who’ve had bar fights and got hit in the eye, airbag injuries, for instance. Anything that has basically direct impact onto the eye can potentially cause that.
Q: How is Vision Loss Defined and Measured?
Andrew G. Iwach, MD: Defining vision, what is it? There actually are different characteristics to how we see. For example, most people will hear, “20/20.” Well, that refers to how sharply you can see print, or let’s say a road sign where you’re driving, but there are other aspects of vision.
For example, the side vision. And why is it important to know that? Well, unfortunately, with glaucoma, it’s often the side vision that gets affected first. That’s where you lose it. In fact, the challenge with glaucoma is that you can lose a lot of side vision and not know about it.
Typically, we walk around with both eyes open, and hopefully, both of your eyes are healthy. And one eye can lose a lot of side vision, this peripheral vision, and you don’t know it. And this is why we call sometimes glaucoma “the thief of vision,” because you’re doing everything right, and you don’t realize that, unfortunately, it’s taking away your vision without you even knowing it.
So those are two common aspects. There are other aspects. For example, your ability to see color or how you see contrast. So there are different ways we measure the quality of vision, but for glaucoma patients, the two most common measurements that we make are the visual acuity — the sharpness with which you see, and we measure the side vision.
Q: How Accurate are Visual Field Tests? Why is it important to have multiple glaucoma exams?
Davinder Grover, MD, MPH: A glaucoma patient understands the way we monitor glaucoma with pressures and imaging and then visual fields. And visual fields are an essential component of glaucoma monitoring. But anybody that’s ever taken a visual field test, myself included, can realize how frustrating that can be sometimes and [how] annoying they can be. They’re not fun, and they’re sometimes miserable and anxiety provoking, right? Because you’re trying to get every one, especially if you’re like me, type A personality, you want to get all the ones and you don’t like the idea of missing something. But some days are good, some days are bad. Some days you’re a little sleep deprived, some days you’re a little distracted, some days you’re thinking about what you want to do right after this exam and it’s hard to maintain focus.
So I tell my patients, I don’t ever get too excited or too worried about one visual field change because if you look back at all the studies we’ve done on visual fields, when you see a subtle change in a visual field, 80% of the time when you repeat it, it goes back to its baseline. So I know it can be worrisome when you’re taking a visual field and you want to do your best and you want to get the best result. Sometimes we just aren’t having a good day and sometimes the visual field is not the most reliable or sometimes it shows a little change. But don’t get too worried or excited unless you repeat it and it confirms that change. But it’s a subjective test and again, there’s a human subjective component. So there’s always some variability. There’s always some background noise. And what we’re looking at is for a trend over time.
The other thing to remember is that when you have a visual field defect from glaucoma, that’s actually when you’ve lost a significant amount of your nerve tissue. So we want to be careful with that and if you have already lost enough nerve tissue where you have a visual field defect, we’ve got to be very careful with you. You can lose a lot of nerve tissue and have glaucoma damage without having a visual field change. So don’t be falsely reassured because you have a normal visual field that everything is fine, you can lose a significant amount of nerve tissue and not actually have an impact on your visual field.
So visual field, as well as electronic imaging of the optic nerve tissue and pressure checks, as well as all of the things that are such important vital signs for monitoring glaucoma. Visual fields are one of the more annoying ones because it’s really not fun to take them, but they are an important thing. Again, do your best not to let every click make you feel that every one [click] matters and if you miss one, it’s done. Because that test is very smart. It knows what you should see. It knows what you may not be seeing, and it’ll go back and test things. And again, your doctor will look at the [visual] field [test results] and if there’s a change, repeat the [visual] field [test] before making any significant change in your treatment plan.
Q: Pregnancy and Glaucoma Treatment
Ranya G. Habash, MD It is possible for a pregnant lady to have glaucoma and also to have a natural delivery. Even if you’ve had glaucoma surgery, it really shouldn’t impact the pregnancy per se. One of the things maybe that we would look out for is if you had a really long delivery and there was a lot of Valsalva or a lot of pushing, for instance, you just want to have your glaucoma filtering surgery checked afterwards just to make sure that it’s still functioning properly. But we have plenty of patients with this type of situation and it really shouldn’t affect a normal birth.
Posted on January 6, 2021 / Reviewed October 20, 2021