3m eye charts 🤔

Yay or nay? I’m really starting to think they’re inadequate for our purposes, and for knowing when to reduce.

It’s too hard to tell subtle differences between different lines at 3m (@Lajos). Should 3m charts stop being recommended or are they of use?

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I think many people lack the space for a 6m chart so it’s a much better than nothing solution. Plus it can track general acuity of course, I was just saying I think 6m chart is more accurate

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i can see an extra line with 3m compared to the 6m Snellen chart, but my final test would be with the optometrist at the shop before changing lenses.

Depends on your purposes, I suppose.

I said on some other thread… I’d dispute there’s such a thing as a 3m chart. It’s just a chart with some letters of different sizes. You can look at it from any distance you like. Just have to be aware of how to interpret the results. A “3m chart” should have letters exactly half the height of a “6m chart” so it’s trivial to convert between the two. (eg if you stand 6m from your 3m chart). Other distances or other chart “sizes” are slightly less trivial.

  • Also valid to pick a line and track how close you have to stand in order to be able to read it.

If you are looking for something to active-focus on, just stand at a distance where there’s some blur, and clear it up.

Wearing normalised, 3m is probably too close to stand, since blur horizon would be of the order of 4m anyway. But could wear differentials and stand a bit closer.

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I was thinking using 3m and norms. Maybe not accurate here :stuck_out_tongue:

Really?? That’s a bit extreme. I’m not gonna go to an opto to decrease 0.25 D

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i’m not sure what you mean, but i will go to the optometrist once I can read 20/20 on the 6m chart and during the phoropter, the shop has this screen that is a meter away but the text visually looks farther, which I believe to be the same as the 6m chart.
I do not rely on the 3m chart to say if am ready to reduce, but rather to help me with active focus.

I only have a 6m and a 2m. The 2m one is of course tiny so I only use it for low light indoor AF from my couch which is more like 3m away, but never for actually measuring.

Blur horizon is not a cut off thing, it’s a range. Especially not in “low myopia”, regardless if you create that condition with eye lenses (so you are low myopic) or with glasses (so you have a normalized on). I would say that it’s hard to interpret blur horizon without specifying the size of the details of the object you watch. So while your “blur horizon” for “20/20 line on Snellen” is 4m with -0.25 actual acuity, it will be lower for “20/10 line on Snellen”. Most likely lower than 3 meter, because otherwise you would be able to read that line :slight_smile:

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I look at my 10ft Snellen from about 12 or 13ft and I find that to be equivalent to my 20ft Snellen

10ft Snellen work fine for improving acuity and sharpness from my experience

Just adding N=1 experience for this:

This has always seemed like an excellent idea, that I’ve yet to properly implement. I somewhat do this with a safety sign at work though.

I mean I think it’s extreme to need an opto to tell you you can reduce 0.25 D. You can decide that for yourself

I guess I still lack confidence in what I am looking :sweat_smile:. I’m not that accurate with the cm measurements because I doubt myself too many times, so my best option is reading a blur line the eye chart. i want to reach 20/20 before getting a new reduced lens because i can have a longer duration with better overall clarity.