Measuring without differentials despite high myopia?

I’ve been struggling with learning to measure. I can never really tell the exact distance when the image starts to get blurry. When I add the numbers to Varikari’s Vision Log Tool the numbers are all wrong.

(I have -0.5 of astigmatism in my good eye, maybe that’s why. Or it could be because I have amblyopia.)

I figured out a way that seems to work for me - measuring without any glasses. I’ve always used my diffs when I’ve tried.

At my level of myopia (I’m currently usring -6.5, -7.5 as my normalized) it’s not ideal. But it is a way of gathering data at least. I’ve been relying on my Snellen chart until now.

What do you guys think? If this is a bad idea, maybe I could buy a pair of really weak glasses, like -2 / -3. There would be a bit more wiggle room measuring with them compared to no glasses at all. Though I won’t be able to know if it works until I’ve tried.

Are you measuring centimeters to blur with a cm tape?

Having a measuring tape thats in centimeters is really nice because you don’t have to convert to another unit of measurement.
Something to keep in mind is how critical consistency is for measuring.

What I do:

  • I use one you’d use for measuring fabric.
  • I have a printed page in a room that doesn’t get daylight. Without consistent lighting, your measurements will be all over the place and you wont be able to trust them. I use the cm side of the fabric measuring tape and move forward and back until I find the edge of blur.

What I don’t do:

  • I don’t use devices or screens to measure. I use a printed page of black text on white paper and find it easier to find edge of blur and more accurate.
  • I once tried using an app that would measure the distance for me but found that is extremely inaccurate for this need.
  • I don’t use Jake’s tape. I didn’t want to fuss with making sure to print to exact scale or tape it together.

Gemily has a video demonstrating how to find edge of blur. You might find it helpful. https://m.youtube.com/watch?v=HBsjw5nBrr8&list=PLwZ22GCkeWqMBMQ9pqpOarAWjRHnVoNFv&index=2

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Yes, I am measuring with a cm tape. I use one for fabric. I just bought a metallic one but I haven’t tried it yet.

I use a printed page as well, it’s always there (I put in on my refridgerator where there is no sunlight affecting it) so I don’t have to turn on the computer or anything. I want it to be as easy as possible. I don’t know if it’s the right size though, I know it’s supposed to be 12 points.

I tried an app as well but it didn’t seem to be working well. The measurements were all over the place.

People keep talking about how important it is to measure so I really want to make it work. It’s actually a lot easier without wearing any glasses, even if I know that it’s not recommended.

I really enjoy Gemilys videos, will watch the video again. :slight_smile: