What is 20/20 vision? The most common practised way to measure vision in a clinical setting is using standard letter charts, called a Snellen chart, with a single large letter at the top and rows of progressively smaller letters continuing down the chart.
In the United Kingdom, the standard placement of the eye chart is on a wall that’s 20 feet away from your eyes. Since many eye doctors’ rooms aren’t 20 feet long, in a smaller room the eye chart may hang behind the patient chair, using mirrors to make it appear in front of you at a simulated distance of 20 feet.
So if you can read the letters on the ’20’ line (which is the green shaded line at the lower end of the chart) from 20 feet away – then you have 20/20 eyesight.
However, most people are able to see better than 20/20. See under our results for more information.
According to the American Optometric Association, “20/20 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance. If you have 20/100 vision, it means that you must be as close as 20 feet to see what a person with normal vision can see at 100 feet.”
The driving standard is 20/40 where the chart letters are twice as big as those on the ’20’ line. If you have to stand at 20 feet away to be able read this bigger letters, when your normal sight friend can still pick them out from 40ft away, then you have 20/40 vision (the red back coloured line on this chart)
Please call us on 0203 733 5657 if you have any additional questions or would like to discuss vision correction in more detail.