Shuchi Patel, MD: Good afternoon, Dr. Ruth Williams. Thank you so much for taking the time to have a discussion with us regarding a topic that is of emerging interest. Today we’re going to talk about the association between blood pressure, blood pressure medications, and glaucoma. Once again, thank you for joining us.
Ruth Williams, MD: Yes, really happy to have this conversation.
Patel: An article that was published this year is the focus and springboard for our discussion today. It was published in Ophthalmology in March 2022 and is titled The Association Among Blood Pressure, Blood Pressure Medications, and Glaucoma in a Nationwide Electronic Health Records Database. The summary of the article was that there has been found to be an association with low blood pressure and an increased risk for open-angle glaucoma. This association was found whether a patient had intrinsically low blood pressure or whether it was medically induced owing to treatment for hypertension. Is that correct?
Williams: Yes, that’s correct. We’ve long known from other large population-based studies that there’s a two to six times greater risk for glaucoma progression in patients who have lower blood pressures, especially lower diastolic pressures. What was unique about this study was the demonstration of the direct effect of blood pressure on the longitudinal rates of retinal nerve fiber layer (RNFL) loss.
Patel: That new evidence was certainly noteworthy. I also found a few other things noteworthy in this study. One interesting finding was that when a univariable analysis between blood pressure medications and open-angle glaucoma was performed, there was a positive correlation with the amount of medications and the class of medications; but when a multivariable association was analyzed, those independent variables were no longer correlated with open-angle glaucoma, and the only factor that had a correlation was a low mean arterial pressure. What do you think this means in terms of the mechanism of glaucoma with hypotension, especially irrespective of use of medications?
Williams: I think what this study did was isolate the effect of blood pressure separately from intraocular pressure. So, when we talk about ocular perfusion pressure, that incorporates intraocular pressure. This study looks specifically at how blood pressure independent of intraocular pressure affects the progression of the glaucoma, which was measured by decreasing RNFL. And as mentioned in the publication, when the correlations were adjusted for age, sex, race, and disease severity, there remained a direct correlation between lower blood pressure and disease progression.
Patel: That is interesting, because if the mechanism for the glaucoma in these patients is just ischemia or poor perfusion, it’s curious to me that, for example, smoking — which should cause some amount of vasoconstriction, and poor perfusion — was not associated with a higher risk for open-angle glaucoma.
Williams: I’m not sure we really know the mechanism of why low blood pressure can cause progression in glaucoma. There are some ideas. For example, a lower diastolic pressure may cause decreased end-organ perfusion. So, could we be perfusing the optic nerve a little less in the face of hypotension? I don’t think we know that specifically, but what’s so interesting to me is that we have long said that the only modifiable risk factor for primary open-angle glaucoma is intraocular pressure. I would argue that these data suggest that at least some aspects of blood pressure is a second modifiable risk factor for glaucoma progression.
Patel: That’s really a good point that you’re bringing up. Until now, the primary factor that an ophthalmologist, especially a glaucoma specialist, focuses on is reducing intraocular pressure, whether it’s with medical treatment, laser procedures or surgery; but we don’t necessarily take a look at the whole picture as much as we really need to be doing. With that being said, have you changed your approach to managing glaucoma, especially as a result of this information that’s come to light?
Williams: Definitely. I’ll give you a couple examples. One of them is that if a patient is progressing and the intraocular pressures appear to be well controlled, I will do a very careful blood pressure history and ask very specific questions, such as, “Do you feel light-headed when you stand up”? or “Has your doctor ever told you that your blood pressures are too high or too low”? I’ll often send people home and say, “I want you to bring back a blood pressure log, and I’m specifically interested in the bottom (diastolic) number.” Patients often come back and tell me the top (systolic) number, but they don’t know the bottom number. So, I’ll say, “Go to Walgreen’s, or CVS, or your corner drugstore, three, four, or five times a week, and get your blood pressure checked, and write down the bottom number.” Surprisingly, it’s very common that people will come back with a low diastolic blood pressure. Often hypertension is overtreated, either purposefully or inadvertently.
By getting a careful history, you can pick up on this, and I’ll tell you one story. I had an elderly lady patient who was very conscientious. She was taking her glaucoma drops, and her intraocular pressures were in the low teens, yet her glaucoma was progressing rapidly. So, I did a careful blood pressure history, and she told me, “Yes, I’m a little light-headed, and when I stand up I have to grab a chair.” I went over her blood pressure medications with her and discovered, with her daughter in the room, that she was taking double her blood pressure medicine dosage. She didn’t know it, her internist didn’t know it, her daughter didn’t know it, but most likely this was the cause of her progressing glaucoma.
The other thing I’ve noticed is sometimes the medication regimen the internists prescribe to achieve a therapeutically low systolic pressure reduces the diastolic pressure even more. Those patients are at risk for progression of glaucoma, too.
Patel: Yes, those are good points, and that was a very good discovery about the double-dosed medication. That correction in medication probably helped the patient not just with her eyes, but probably also helped reduce her fatigue by having light-headedness and maybe decreased her fall risk, improving her overall lifestyle.
Williams: The other thing — and again, I don’t have any evidence for this comment — but when I see cases like this or think about it, I think of end-organ perfusion and I think, “If she’s not getting enough blood to her optic nerve, presuming that’s the etiology of the progression, she’s not perfusing some of her other end organs as well.” So that’s a concern to me.
One remarkable point is if you look at the recommendations for treatment of blood pressure, there’s some controversy in the internal medicine space about how low we should get the pressures. Recently, some internists and some cardiologists have been more aggressive in treating blood pressure.
Patel: Yes, that’s true. I think they have lowered the cutoff for diagnosing hypertension and lowered the target range for those being treated. If these low blood pressures are the culprit for some glaucoma progression, do you think that low-tension glaucoma and the progression of open-angle glaucoma, in the setting of low blood pressure, may represent the same disease process?
Williams: It’s possible. I’m glad you brought up low-tension glaucoma, because when people have low diastolic pressure, what’s our response to that? If it’s a nonmodifiable low diastolic pressure, which it often is in our patients with normal-tension glaucoma (NTG), then what do we do? We respond by trying to lower the intraocular pressure. So, that’s our approach, getting the intraocular pressures down even into the single digits if we can. But one thing we don’t know with our patients with NTG is what their pressures are during the 24-hour cycle, or on those multiple days and months when we’re not seeing the patient.
So when a patient with NTG is having disease progression at low pressures, the question remains: Is the progression due to pressure-independent factors, or is the disease progressing because of pressure-dependent factors? A new practice pattern I have incorporated to differentiate the two has made such a difference in these patients. I now request that the patient rent an eye tonometer and check their pressures at different times of the day for 2 weeks. I’m most interested in the pressure early in the morning in some of these patients, as I have seen early morning spikes.
Patel: That’s a novel approach. I remember my fellowship director and mentor telling me that in his training they would keep patients overnight just to be able to do diurnal pressure readings, to get a better understanding of the cause of progression. To be able to rent a tonometer such as an iCare and take it home sounds like a genius idea because it is a simple thing for patients to learn to use and is safe, with very low risk for harm, yet so much information can be gathered that can really help guide treatment. Can we get information from you as to how we can guide patients on where to rent an iCare?
Williams: The website is called myeyes.net. Unfortunately, insurance usually does not cover the cost, so there is an upfront cost to the patient.
Patel: This information wraps it up really nicely for us in the sense that home monitoring of both blood pressure and ocular pressure may be our best way to come up with a comprehensive plan for our patients with glaucoma that is progressing. The information we get from this will help us decide if we need to be more aggressive in lowering intraocular pressure, or if we have to start looking at variables that are independent of intraocular pressure, such as blood pressure, and altering blood pressure control.
The take-away point for me from today is that as glaucoma specialists, we to have to expand our focus outside of the eye and include variables such as blood pressure into the equation.
As ophthalmologists, we can work with primary care physicians and cardiologists to determine optimal blood pressure from all standpoints.
Williams: Definitely; you said it well. I’d say all the pressures matter.
Patel: That’s a great way to say it. Thank you so much for your time, giving us your opinions, and guiding us on some of these newer options for home intraocular pressure measurements that are now available. With these new findings and options to help our patients, I hope we can optimize the care we provide.
Shuchi B. Patel, MD, is director of glaucoma services in the department of ophthalmology at West Palm Beach VA Medical Center in Florida. She explores the ever-changing glaucoma space for Medscape, including advances in diagnostics and treatments.