2020 is upon us – with pretty much every optical establishment (and plenty of other businesses!) in the country jumping on the marketing opportunities (and puns) that this year provides us with. Rather than churn out the standard ‘we’ll make sure you have 20/20 vision in 2020’ phraseology, we thought we’d explain what 20/20 Vision actually is. And then leave it there.
What is 20/20 Vision?
First of all, it’s not ‘perfect’ vision. It’s a measurement of Visual Acuity using a scale created by the Dutch opthamologist Herman Snellen in 1862.
Visual Acuity. It’s how clearly you can see something. It’s part of what we test during an eye examination but not the be all and end all. We also look at the health of your eyes, your peripheral (side) vision, your colour vision and a host of other things.
The Snellen Chart
Herman Snellen created the chart of letters that we all associate with an eye test – the one of (usually) 11 lines with the huge letter at the top going down to the really tiny letters at the bottom. Snellen created special characters (optotypes) and placed them set distances apart (lots of physics going on) and used these to assess how clearly people could see them.
20/20 vision was his definition of ‘normal’ – being able to see a certain size of letter (or thing) clearly from 20 feet away. This was the 8th line down on his chart. 20/20 vision was made metric as 6/6 (6 metres) vision – but obviously that doesn’t work so well with years like this one!
Opthamologists still use the principles of the Snellen Chart which has developed into a LogMAR chart which measures things in a slightly different and more accurate way.
As a guide though, if you have 20/100 vision, you need to be 20 feet away from what a ‘normal’ person can see clearly from 100 feet away – so 5x closer.
Can you have 20/20 vision and still need glasses?
Oh yes. As we get older, our clarity of vision at 20 feet can still remain ‘normal’ but our vision close up (reading, close work etc) deteriorates (see our post on varifocal sunglasses) and we need reading glasses.
You might need glasses for another aspect of your eye health too and, to answer one of our most frequently asked questions, you can have EnChroma® glasses with non-prescription and prescription lenses
20/20 in 2020
We promise this is our last mention of it! If you can’t see clearly and/or haven’t had an eye examination for a while, pop in or give us a call and book an appointment. It might just be that your glasses need a really good clean (we’ll do that for free), that it’s time for some reading/varifocal glasses in some extremely cool frames or that your prescription has changed. We’re here to help.