The Glass and the actual dpt in it - starting point for normalized

Hello everyone,

I am looking for the starting point for my normalized. I would like to take my current glasses as benchmark, as one would do. I have run into somewhat of an annoyance, maybe someone can help.
Is it possible that two of those machines that measure the refraction of the glass in the spectacles give different readings?
In my case:

-8.00 dpt and 0.25 cylinder
-7.25 and 0.25 cylinder
(as measured by optician last week)

-7.75 and 0.25 cylinder
-7.00 and 0.25 cylinder
(this is what I was sold couple years ago, as I checked on the little paper that they gave me with them)

I went to an optician this morning to ask about this and maybe have him check the glasses with his machine. He wasn’t helpful as I had not bought the glasses in his shop. All he said was: “Mmmh… It doesn’t really matter with your high prescription.”

Well it does matter if I want to reduce 0.25 dpt… any ideas?

Thank you in advance =)

Nor was mine more than a year ago. He read my glasses, but kept the printout close to his chest and would not give it to me.

Are these the ones you asked him to measure? It looks like they would do as norms.

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I can imagine! oh my…

Jup, when i started they had become a little too weak for me but I can read everything on the Snellen now (except for the last line) and was confirmed that the strength is perfect by the optician last week. So I thought I should be thinking about getting new normalized in a couple of weeks. I just don’t know what to take as a baseline when I want to go a step down… I am going to try another optician this afternoon, but it’s not a nice experience going in at all. I’ll try one of the large chains, I hope they won’t take my request as personal and just book it under “customer service” to fulfill my wish of wanting to know what exactly I have in front of my eyes… :wink:

Is it a 6m Snellen, and what is the last line you have on it? On mine it is 20/10. Being able to read a Snellen line is not the same as being able to see all the letters on that line without any blur. I can read the 20/20 line on mine without any glasses, but that does not mean I have 20/20 vision. I can even make out the 20/15 line on it in best light, but that still doesn’t mean I have 20/20 vision. My naked right eye’s distance to blur on small printed text still puts me at -0.75, if not a little more.

My snellen stands at six meters. 20/10 is the last line on mine, I can’t read that. The tiny print gets tricky at very high myopia with glasses. But I did do an eye-test at the optician who confirmed that I had the correct strength in the glasses.

So reducing should just be a question of deciding whether you can handle a 0.5 D reduction (at high myopia) or want to be cautious with a 0.25 one. Considering the cost of glasses at high diopters, I would have been tempted by a greater reduction rather than a smaller one. But I cannot see through anybody else’s eyes. Good luck.

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With higher diopters, if they don’t read the lens exactly through the optical center at the right angle they can get off readings from the machine. The script should be more accurate for buying similar lenses. But you’re below -10, you should be able to to take your own cm measurements to confirm your sphere.


Issue resolved… went to the other optician and he was really friendly and checked the glass. Even showed me the machine, explained and let me see the measuring for myself. The reader jumped between 7.75 and 8.0, which can happen if it’s like a 7.82 or something. Depending on the exact way you place the glass in the machine it can give one or the other reading. So I will just stick with the measurements I saw with my own eyes today :wink: … and obsess about the reducation I have worn my differentials for the full six weeks.


ah, we posted at the same time. That is exactly the case!

taking my cm is another thing. My edge of blur for close up is 16 cm, which leaves me at -6.25…

jup, exactly… i will mull over it a little more.

How about trying your previous pair of glasses as norms. What line of the Snellen can you read with them?

Edge of blur can be deceptive, as per another thread recently started by Denise. It took me a long time to be able to decide on this with any certainty, and I am still not really certain about it, other than that it improves, which is what matters.

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If you need to apply a vertex correction for glasses, that may take you up to -7



using 0 to 13mm, that comes to -6.8. If we’re talking about your good eye that’s prescribed -7, that lines up perfectly with prescription +0.25.

You’re starting to get into the range where glasses are a little more expensive and you might not want to order a lot of pairs of high index to figure out what you need. Some optical flippers are cheaper than a full test lens kit, a 1, 0.5, and 0.25 would be all you’d ever need to figure out norms and differentials from your current glasses.

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great tips, thank you! i really appreciate it :heart:

I had hte same experience: what was measure years later in a shop and what was on my prescription did not match. So either they increase the prescription a bit for manufacture, or the reading machines are not accurate