Variability in three successive IOP measurements - why?
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6 months ago
@member_31

Often 3 iCare measurements one after another, can give me IOP values of 19, 17 and 14.

If I expect that when I measure 14, the next measure could be 19, it often it turns out to be true.

For the people that measure IOP at home, does that happen to you?

Should I be coming up with some median eye pressure then?

I think I've brought this up before, but I need to explore it further.

icare-tonometer self-tonometry iop:intraocular-pressure • 321 views
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6 months ago
david 3.9k
@david_fe

I think I've brought this up before, but I need to explore it further.

Yes, that's worth exploring. If you want the FitEyes group to help you explore it further, please provide actual data with the timestamps and the conditions. (See more below.)

Often 3 iCare measurements one after another, can give me an IOP of 19, 17 and 14.

Without any further info, that could simply be due to you progressively relaxing.

So I can expect that when I measure 14, the next measure could be 19.  And often it turns out to be true.

The mind's influence on IOP can be substantial. But you also need to say how much later that next measurement is and describe the conditions.

Then you need to do an experiment and record the actual results. Saying "it often turns out to be true" is not enough. When you try to replicate this, did it happen 3 of 10 times or 8 of 10 times, for example?

If you think something is true, test it and collect the data. See if you can prove it is true (with data).

Without the actual data and more details from you, it will be hard for us to tell you exactly what is happening in your case.

For the people that measure IOP at home, does that happen to you?

Yes! In my own case, numbers like this are definitely due to me relaxing after the initial measurement. I have tested this carefully, and I can replicate it. Seeing this pattern also helped me learn how to manage my IOP better to avoid the "19's" and have more "14's".

You can vastly improve your mastery of how to manage (or simply understand) your own IOP with the help of self-tonometry by paying attention to the details. Treat it like a game or a puzzle. For example, when you are solving a complex puzzle, you cannot do it well if you don't pay attention to all the details. You also can't play a game if you don't know the rules. It's the same here. Exact timestamps and details of the conditions (often including what you are doing, thinking, feeling, or what preceded the measurement) are important.

Here's one blog on this topic:

Detective Work Required - Eye Pressure Going Up While On Relaxing Vacation | FitEyes.com


Should I be coming up with some median eye pressure then?

It depends on your goals. Here's a related question on Ask FitEyes:

What Are Examples of the Different Approaches to Home Eye Pressure Monitoring? | Ask FitEyes

If you want to understand your IOP deeply and improve your ability to manage it, do not simply average out these differing values! That approach represents a loss of clues to solving the puzzle, to use my analogy. The way you worded your question implies that you do want to understand this as well as you can. To do that, don't ignore the details. Coming up with a mean or median IOP is a process of "ignoring" details.

On the other hand, if your goal is just to monitor, then yes, maybe you can just average your IOP (such as for the entire day), provided none of the individual measurements are above a safe threshold for you. There is nothing wrong with any of the different approaching to self-tonometry. Pick the one that is right for you. But if you pick something close to casual monitoring, please recognize that other people usually won't be able to give you answers about the details of your own IOP, because neither you nor they have those details.

For more on this topic, look up the posts by engrav on Ask FitEyes, as one good example.

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Thank you Dave. I'll provide the data.

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6 months ago
BrianB • 230
@brianb

I have seen this a few times in the 10 months I've had mine, but it's only been due to:

  • batteries needing to be replaced
  • probe is bent or worn
  • the base is dirty

.. otherwise, mine are very consistent

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Who knows maybe I'm doing something wrong. How often do you replace the probe? What base and how do I check that?

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Regarding the base, look in the user manual, if you still have it. If you unscrew the black ring that holds the probe assembly in place, there is a long, thin base that slides out. You should have gotten a spare one. The cleaning instructions are to soak for (I forget how long) in 100% alcohol (as I recall). I do that every couple of months.

I wanna say I use my probe for maybe a month or so? I don't really keep close enough track of that. But I also have a Reichert, so I don't use the Icare every day

Having to replace the batteries was a bit of a surprise. I would have thought they would last longer (I think they started to fade at like 8 months)

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silentsneg - Brian is correct. The probe base needs to be kept clean. I clean and rotate mine about once a week. (Since Brian is not using his iCare every day, he can get away with less frequent cleaning and replacing probes.)

BrianB - I use 70% or 91% isopropyl alcohol. I have never found 100% for sale in US stores. Don't soak too long or the items will corrode. (I soak/clean and reuse my probes too, but those will wear out after a while.)

I wanna say I use my probe for maybe a month or so?

At one end of the gradient, iCare recommends using a new probe for each IOP exam. At the other end of the gradient would be using a probe for a month. Most FitEyes users are in between. Most use the probes anywhere from several IOP exams to over several days -- and maybe up to a week or two.

Keeping the batteries fresh is very important. How long they last depends on the batteries and the amount of exams.

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