Most people will have heard of the term 20/20 vision, however, it’s likely that many people aren’t entirely sure what this means. Simply put, 20/20 is a measurement of visual acuity (clarity of vision) based on the Snellen chart – the chart of letters of progressively smaller size that is used in standard sight tests.
Based on the Snellen visual acuity system, the top number in a visual acuity fraction is the distance at which a certain line of letters on a Snellen chart are viewed. In the USA, this is measured in feet, whereas in Europe, where metric units of measurement are standard, this is measured in metres. The bottom number of the fraction refers to the distance at which a person can see a certain line of letters clearly, so 20/20 (or 6/6) means that are person can view the chart clearly from 20 feet (or 6 metres) away.
Is 20/20 perfect eyesight?
20/20 is considered to be normal eyesight but is not the best possible eyesight. A person with 20/15 vision can see letters clearly at 20 feet that a person with 20/20 vision could only see at the same level of clarity from 15 feet away. In contrast, when the bottom number of a visual acuity fraction is larger than the top, this corresponds to worse visual acuity. For example, a person who has a visual acuity of 20/40 or 20/80 cannot see as clearly at distance as a person with 20/20 vision can, and a person with 20/200 vision is considered legally blind.
It’s practically impossible to define what ‘perfect’ vision is, as different levels of visual acuity can be better suited for different situations.
Visit your optician
To ensure your you are comfortable with your eyesight in all situations, it’s important to see your optician for an eye examination. We recommend that you should have your sight and eye health examined by an optician at least once every two years (or more regularly if your optician advises so).
If you experience problems such as eye strain, blurred vision, or difficulty adjusting to changes in light, these are signs that you need to schedule an eye examination as soon as possible.
To book an eye examination at Dominic Tunnell Opticians, please call us on 01905 950222, or visit us at 6 Mealcheapen Street, Worcester, WR1 2DH.