What is 20/20 or 6/6 Normal Vision?

Most people who require vision correction – and even most people who don’t – will be familiar with the term “20/20 vision”. While this term is widely used and is universally understood to mean a person has good vision, many are unaware of what these numbers really mean. So, what is “20/20” or “6/6” vision? Let’s find out.

The Snellen Chart

If you have ever had an eye test (it is recommended you have one every two years!), you will probably be familiar with the Snellen chart, even if not by name.

This common eye test – also known as the Snellen scale – is used to measure a person’s visual acuity – that is, how well you see objects at a distance. It features several lines of letters, each getting smaller as you move further down the chart. Your optometrist will place the chart at a distance of 20 feet (or 6 metres) and ask you to read these letters aloud until you get to a line on which you can no longer distinguish the letters.

Each row of the Snellen chart represents a measure of visual acuity. For example, the top line is the “20/200” line: this means that the reader can discern at 20 feet what a person with “normal” visual acuity can see at a distance of 200 feet. If a person is unable to discern letters below this line on the Snellen chart, with correction, they are considered legally blind.

20/20 Vision

The “20/20” line (or the 6/6 line, if you are in the US) appears further down the chart. Being able to discern the letters on this line means that you can see at 20 feet what a person with normal visual acuity can see at 20 feet; in other words, you have average vision. At this distance, the symbols on the line representing “normal” acuity on the eye chart, designated 20/20, is the smallest line that a person with normal visual acuity can read at a distance of twenty feet.

Three lines above, the letters have twice the dimensions of those on the 20/20 line. The chart is at a distance of twenty feet, but a person with normal acuity can read these letters at a distance of forty feet. This line is the ratio 20/40 (or 6/12). If this is the smallest line a person can read, the person’s acuity is 20/40.

In this short 35-second video, Mr Glenn Carp explains what 20/20 and 6/6 mean:

Mr Glenn Carp – “The main concern of having 6/6 vision or 20/20 normal vision really comes from whether you are based in the United Kingdom or you are based in America. It is really just to do with feet and metres. 6/6 means you see at 6 metres what an average person can see at six metres, and 20/20 is the equivalent in feet, twenty feet versus twenty feet. So the average normal vision in the general population would mean that what someone sees at twenty feet an average person can see.

“If you have better vision than 20/20 for example 20/16 it means that you can see at twenty feet what an average person can only see at sixteen feet and of course the opposite if you are 20/40, for example, it means you have poorer vision than an average person; you see at twenty feet what they see at forty feet from much further away.”

How you can achieve 20/20 or 6/6 normal vision or better

As Mr Glenn Carp explains above, while 20/20 vision is usually considered a sign of good vision, it is possible to achieve better than this standard of visual acuity. This is the case if you are able to distinguish the letters on the lines below the “20/20 line”. Some people have 20/16 or even 20/12.5 vision, either with or without correction with visual aids or treatment.

For example, 97% of our short-sighted patients achieve 20/20 or better after surgery (which includes patients who see 20/16 or better, and patients who see 20/12.5 or better).

Many people with refractive errors have the misconception that they have “bad vision” because they “cannot even read the E at the top of the chart without glasses.”  However, in most situations where acuity ratios are mentioned, they refer to best-corrected acuity – that is, the visual acuity achieved when you are wearing glasses or contact lenses.

Furthermore, many people with moderate myopia (short-sightedness) are unable to read the “E” at the top of the chart without glasses but have no problem reading the letters on the 20/20 line with appropriate visual aids. In contrast, a person who is legally blind will be unable to read the top line of the chart even with correction.

What are my chances of achieving 20/20 vision with Laser Eye Surgery?

The primary aim of Laser Eye Surgery is to correct a patient’s vision to the same standard as they previously achieved with glasses or contact lenses. In other words, to achieve your “best-corrected visual acuity” – or better. Your optometrist or surgeon may refer to “gaining or losing a line of vision” when discussing your visual acuity outcomes; this refers to the change in your ability to read the lines on the Snellen chart without glasses after your Laser Eye Surgery, compared to your ability to read the line with glasses, before surgery.

As Mr. Glenn Carp explains in the video below, your chosen clinic should be able to provide you with an idea of how likely you are to  achieve 20/20 vision with Laser Eye Surgery.

At London Vision Clinic, 98% of our short-sighted patients (with a prescription up to -12.0D), and 93% of long-sighted patients (with a prescription up to +7.25) achieve 20/20 vision with Laser Eye Surgery. 

If you would like to learn more about the results you could expect from Laser Eye Surgery, or to find out more about our results, get in touch with one of our friendly clinic coordinators. Alternatively, to start your journey to clear vision, Book a Consultation today.

Laser Eye Treatment Fees start from £6,200 for both eyes. Very complex treatments may cost more.

Interest-FREE finance available over THREE years, from £87 per month for both eyes, makes the best more flexible. Find out more.