Monitoring IOP Fluctuations to Manage Open-Angle Glaucoma
Joseph F. Panarelli, MD: We know that fluctuating IOP poses a significant risk factor for visual field progression and high fluctuations result in greater visual field loss. What have you seen in your own patients?
Sahar Bedrood, MD, PhD: In my practice there are a subset of people who have very, very steady IOPs every time I see them, and then there’s a subset that fluctuate as little as 4 or 5 mmHg, and they get huge rates of progression. And then I have patients who have fluctuations as high as 20 mmHg, but they don’t have progression as fast. I can’t quite make sense of why all of that happens. I can, however, tell you that their genetic predisposition is important. So if I see a patient whose father went blind with glaucoma, and then they are having these small fluctuations, I really want to get their pressure low.
If I have patients who have other comorbidities that require injections with anti-VEGF, then I might be a little bit more forgiving in some senses, but I’m also watching out, because they might fluctuations as high as 20-, 30-, or 40 mmHg, which is really scary when you’re seeing them, but in actuality they can tolerate it a little more.
So all in all I do have patients with wide range of fluctuations. I’m very, very aware of that and I kind of customize it to each patient depending on how aggressive their glaucoma is, and if they have any other eye comorbidities that I should be aware of.
Dr. Panarelli: In your practice, do you typically get a single IOP reading or do you take multiple readings?
Dr. Bedrood: In my practice I typically get two IOP readings. One is with an iCare tonometer done by my technicians, and one is applanation done by myself. And they’re usually very similar. If they’re not, I stick to my applanation reading.
But interestingly when I was in Fellowship we did a small project amongst the Attending physicians where all the Attending physicians had applanation, and all of them were off just by a little bit – 1- or 2 mmHg. So user variance is something that should be thought about and considered when you’re doing the applanation. And so I trust my readings when I’m measuring them. If my Fellow is there, she will trust her readings when she’s measuring them, and those are kind of what we go by. But truly I think two different modalities of measurement is a nice way to make sure you’re getting the correct reading.
Dr. Panarelli: What do you think are the presumed causes for these fluctuations? Is it disease progression? Is it more related to compliance?
Dr. Bedrood: The presumed reason for these fluctuations can be multiple things. One is poor compliance. Of course we can always blame it on that, right? Patients sometimes don’t take their drops on time, or ever. The other thing is poor response over time. So sometimes patients respond really well in the beginning and then over a couple of months or years they don’t, and then they fluctuate their IOP.
The other is kind of a genetic component. Some patients naturally will fluctuate. They make more aqueous so they don’t drain at certain times of the day. And so those fluctuations are significant and we have to kind of customize it for each patient.
Dr. Panarelli: What trends can be observed with 24-hour IOP monitoring? What information can clinicians gain to better manage and treat glaucoma?
Dr. Bedrood: Diurnal fluctuations between 2 and 4 mmHg are pretty normal throughout the day. These fluctuations can be great or greater in some of our glaucoma patients. We also know that erratic fluctuations can be common. And in that diurnal fluctuation you usually have early morning spikes, and then it’s a little bit lower in the afternoon.
Some of the other things that we consider are supine positioning. So when patients go to sleep there’s actually more pressure and they can have an increased pressure when they’re in the supine position.
Dr. Panarelli: What products are in development or are currently available that provide clinicians with better monitoring capabilities?
Dr. Bedrood: Currently in addition to what we have in the office, we also have things that patients can take home with them. So at-home IOP monitoring devices, they can actually use that. It’s not very commonly used. I think financially it’s difficult for most patients to purchase it. I think there’s a rental version for some people. And some physicians have found it beneficial because you can see things that you don’t see in the office. Like maybe they have an afternoon or an evening spike that you’re not catching. So I think that there is some value in it, and I think the future of glaucoma is to be able to monitor these. Maybe not with at-home devices, but maybe implants or some kind of self-regulatory manner. But the future is to be able to maintain a steady IOP for these patients.
Dr. Panarelli: How can clinicians identify and better control interval fluctuations?
Dr. Bedrood: The home monitoring devices can measure some of those IOP fluctuations. Whether we can control it, not really. We can’t control anything from the distance, right? I think surgical intervention is the best way to right now currently to control something so we have a steady state. But otherwise, the at-home monitoring devices are currently what you can use.
Some of the other advice that I have seen being given is to tell the patient not to push on their eye, especially when sleeping. They can actually physically put some pressure on the eye and that can increase the pressure in certain patients. And so those are some of the things. It’s very hard to control pressure from afar or during the evening, but we certainly can monitor it.