What Is 20:20 Vision?
Do your friends brag to you about their 20:20 vision? You know fighter pilots have it, but do you know exactly what it means?
Is it really the badge of honour you think it is?
Well, not exactly.
What Does It Mean?
20:20 is a term used to describe normal vision, sharpness and clarity at a distance of 20 feet. Since we stopped using imperial measures, though, it would be more accurate to call it “6:6 vision” – tested at a distance of 6 metres.
It is a measure of visual acuity and is the yard-stick against which we measure varying levels of eyesight. It is traditionally measured by your ability to identify black letters of varying sizes on a white background, from a standardized distance – the Snellen’s Test.
For driving, the DVLA require you to be able to read the third line up from the bottom on the Snellen’s test – 6/9 vision. But don’t worry, this can be done with glasses or contact lenses too!
The Snellen Test was invented by a Dutch ophthalmologist Herman Snellen, in 1862. Incidentally, Snellen was a hunter, and so valued distance above all else! It is only one measurement of sight, and one we carry out alongside other more in depth measurements in our eye test.
Contrary to popular belief, 20:20 doesn’t mean perfect vision.
20:20 indicates sharpness or clarity at a distance, but doesn’t take into account other elements of your eyesight – peripheral vision, depth perception, eye coordination or colour vision. For example, some people see well at a distance, but struggle to focus on nearer objects, while others have excellent near sight, but struggle to see things far away.
Distance is not the only measure of sight.
Less than 20:20 vision can be easily corrected using glasses, contact lenses or corrective surgery. To make sure you’re seeing things as clearly as possible, it’s important to have your eyes tested every 2 years to test all aspects of your vision and eye health.
If you have noticed a change in your eyesight, or think that your vision may need correcting, make an appointment with your local optician today. We have branches in Cardigan, Narberth and Pembroke Dock and use the latest ophthalmic testing equipment.
Things have come on a little since Snellen’s day!