20/20 vision is a term used to express normal vision or normal visual acuity (how clear or sharp your vision is). If you are lucky enough to have 20/20 vision without any corrective eyewear, it means that you are able to see things clearly at 20 feet away what should normally be seen at that distance. In other words, someone with 20/20 vision can see what an average person can see when they are standing 20 feet away.
If you have been to the optometrist or ever had an eye examination (which you should be getting regularly!), you will be familiar with the Snellen eye chart, like the one pictured above. The chart was named after Herman Snellen, the Dutch ophthalmologist who created this system in 1862. Eye charts like these are used to evaluate what an individual’s visual acuity is.
Notice the numbers on the extreme right side of the chart, such as 20/40 and 20/70? They are the visual acuity measurements, also called Snellen fractions. The number on the left of the “/” symbol is your distance in feet from the chart, kept constant at 20 feet (or around 6.1 metres). The number on the right of the “/” symbol is the distance at which a person with normal eyesight can read the letters in the same line. For example, if you have 20/50 vision, it means that your vision is worse than average and that at twenty feet away, you can read the letters that most people can read from 50 feet away.
20/20 vision is NOT perfect vision
20/20 vision is just the visual acuity of the average individual. It is possible to have a visual acuity that is better than 20/20! 20/15 vision, for example, is better because it means that at 20 feet, you can see clearly what a normal individual can only see from 15 feet away.
Also, bear in mind that having 20/20 vision does not mean that you have perfect vision, because the measurement is only a sign of clarity of vision at a distance. Other measures of sight like peripheral vision, depth perception, colour vision and more make up the total visual ability of an individual.
If my vision is less than 20/20, what can I do?
If you are not able to see your surroundings clearly, you should visit your eye doctor as soon as possible to ascertain what eye condition you might have. In most cases, you should be able to get corrective eyewear like prescription spectacles or contact lenses that would be able to restore your corrected vision to 20/20.