2.9 years ago

Daywalker • 240

@_245

So, something that I see mentioned over and over in forum discussions is “low blood pressure”.  Does anyone here know what is meant by low blood pressure?  I know the normal blood pressure range according to the American Heart Association is anything less (<) 120 mmHg for Systolic and < 80 mmHg for Diastolic.  They don’t define “low”.   I have seen some other sites like Mayo Clinic mention low blood pressure (which they call hypotension) is Systolic < 90 or Diastolic < 60 mmHg.

So, in the context of a glaucoma patient, what is considered low blood pressure?  I say “in context” because we know low blood pressure can be bad for glaucoma patients since it lowers their ocular perfusion pressure, especially overnight.  For a person who does not have glaucoma, then low blood pressure may be fine.

2.9 years ago

david 4.3k

@david_fe

For a person who does not have glaucoma, then low blood pressure may be fine.

Yes, you have that right. This concern needs to be addressed in the context of glaucoma.

So, in the context of a glaucoma patient, what is considered low blood pressure? I say “in context” because we know low blood pressure can be bad for glaucoma patients since it lowers their ocular perfusion pressure, especially overnight.

You have essentially already answered your own question. The answer is that one's intraocular pressure will determine what level of blood pressure is too low for you. Anyone with a tonometer and an automatic home blood pressure monitor can check the relationship between their IOP and BP.

Since you already know that the answer must be "in the context of glaucoma," we can readily see that we must also know that individual's IOP before we can answer, "what blood pressure values are too low for me?"

I suggest you calculate what is often called "diastolic perfusion pressure" (DPP). It is done as follows:

Take your diastolic blood pressure minus your IOP at that moment. This is your DPP and it is a value you can compare to a threshold. The threshold is typically 50 or 55 mmHg.

Let me quote from this study :

a low diastolic perfusion pressure, under 50−55 mmHg, was associated with glaucoma prevalence in epidemiologic studies conducted in the United States, Europe, and the Caribbean

The obvious next question is, what do I do if my DPP is less than that threshold? You can either raise your BP or lower your IOP.

However, raising low blood pressure (to improve DPP or for any other reason) is typically very challenging. Donald L. Budenz, MD, says:

“Any time you lower eye pressure, you’re improving perfusion pressure. It’s easier to lower IOP than trying to raise blood pressure. If blood pressure is low in an individual patient, consider more aggressive IOP therapy.”

That may be a sufficient answer for many of us -- keep focusing on managing our IOP. I do have low blood pressure and I have tried every solution I have heard of without success. But I was able to lower my IOP significantly via self-tonometry. So I tend to agree with the Donald L. Budenz, MD quote above.

The following article is an interesting read if you want to dive more deeply into this topic:

The Ins and Outs of Pressure Gradients https://www.reviewofoptometry.com/article/the-ins-and-outs-of-pressure-gradients