You’ve heard of the phrase “20/20 vision”. But what exactly does it mean?
To put it simply, 20/20 vision refers to someone’s visual acuity — the clarity or sharpness of vision — measured at a distance of 20 feet without vision correction such as glasses or contact lenses. So, if you have 20/20 vision, you can see clearly at 20 feet, which is the normal distance for most people.
Visual acuity is usually measured with a Snellen chart. Snellen charts display letters of progressively smaller size. The first number shows your distance from an eye chart. The second number shows the size letter you can read. 20/20 is Normal vision. It is the minimum vision required to be a fighter pilot or to read the stock quotes in the newspaper, or phone numbers in a telephone book.
So, why is 20 feet the chosen distance? When you’re looking at an object 20 feet away, your eye is relaxed in its normal shape. It does not have to bend the light rays from the object to focus the image on the retina in the back of the eye. To see objects closer than 20 feet, the lens must bend the light rays.
For example, 20/30 denotes vision problems. Though you’re 20 feet from the chart, you read letters which most people see when they’re farther (30 feet) from the chart. On the other hand, 20/15 shows sharper than average vision.
Having 20/20 vision does not necessarily mean you have perfect vision. 20/20 vision only indicates the sharpness or clarity of vision at a distance. Other important vision skills, including peripheral awareness or side vision, eye coordination, depth perception, focusing ability and colour vision, contribute to your overall visual ability. Only about 35 percent of all adults have 20/20 vision without glasses, contact lenses or corrective surgery. With corrective measures, approximately 75 percent of adults have this degree of visual acuity.
Worried about your vision? A proper eye test by our optometrists can diagnose what is affecting your ability to see well. Book an appointment by calling us on 9362-9944 or book online.