2.5 years ago

Merilee • 10

@merilee

I've had my tonometer for a few weeks now, a Homecare2. I've noticed a difference of 1 or 2 points between dry vs. using lubricating drops. I do this at the same time. First without putting lubricating drops in and then putting them in. I'm just wondering which way is more accurate? Thank you.

2.5 years ago

david 4.3k

@david_fe

I'm just wondering which way is more accurate?

If you have extremely dry eyes, your tonometer will be more accurate with the lubricating drops. However, lubricating drops are not needed by most people in order to get accurate results from a home tonometer.

I've noticed a difference of 1 or 2 points between dry vs. using lubricating drops. I do this at the same time. First without putting lubricating drops in and then putting them in. I'm just wondering which way is more accurate?

For background, please see this post:

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

A difference of 1 or 2 points is well within normal fluctuation. For example, some people will see a reduction of 1-2 mmHg on a subsequent measurement simply from relaxing.

The small difference you are seeing might not be related to using lubricating drops.

To help eliminate confounding effects, can you say more about your methodology? For example, I suggest you could test as follows:

1. test your normal way
2. test using a control where you do all the same steps in the same sequence but you don't actually instill the lubricating drops. (Maybe use an empty container so you can go through the motions.)
3. keep extremely good notes of each and every test
4. don't ignore any test results (e.g., because the data isn't what you expected)
5. do your best to counter the placebo effect; it's impossible to avoid entirely, but you could get creative. (I'll share further ideas below.)
6. repeat at least 15 times each way (normal and "control")
7. share your data -- maybe one of us could run a statistical analysis if you can't do that yourself.

In regard to the placebo effect, since you now know that relaxing (especially relaxing your facial muscles and breathing in a relaxed way) can often reduce intraocular pressure 1-2mmHg (or more), for your control, you could do a minute of relaxing. Then you could compare the lubricating drops against the minute of relaxation. If using lubricating drops shows lower IOP on the subsequent measurement compared to the "control" (relaxation), that's a strong indicating the lubricating drops are working for you.