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Seraphiel0
2 years ago

Dioptrics are not the only way to measure the vision. In the USA, zb is a system that compares vision with how someone sees healthy something that is 20 ‘feet’ away. So zb, someone who has a ’10/20 vision’, sees something that is 10 feet (ca 3 m) away is as good as a healthy something that is 20 feet (i.e. about 6 m).
Or, one measures in percent compared to a healthy one.

Or, you don’t even measure. The optician just has different strengths there, you go in, try out all the strengths and the one that is best, you take with. Whether they are now called dioptrics or with any invented units that they are numbered zb, it really doesn’t matter.

The SI units are not the only one that exists – even if it is a damn good system.