Your life and eyes 2 min read

What Does 20/20 Vision Mean?

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You have no doubt heard the phrase ‘20/20 vision’ before. It’s often said when someone is talking about having perfect vision, but what does it actually mean? To understand the meaning of 20/20 vision, it’s important to know more about visual acuity and how it is measured. If you’ve been for an eye examination before, you will be familiar with the eye chart that features lines of letters in varying sizes. This is often known as a Snellen chart, named after the ophthalmologist who invented it. The Snellen chart is at the centre of measuring your visual acuity and how clearly you can see.

Measuring your visual acuity

Your visual acuity refers to the clarity of your eyesight, and it’s measured by your ability to see the letters on the eye chart from a specific distance. There are a number of factors that can affect how clearly you can see the letters. The first is how accurately the cornea and lens of your eye can focus light on the retina. The second is the sensitivity of the nerves both in the retina and the brain, and thirdly the ability of the brain to interpret the information received.

optician during they vision check

20/20 is a fraction to explain your visual acuity measurements. This is actually an American measurement, and in the UK and Ireland it’s known as 6/6. The first number refers to the distance between yourself and the eye chart, which is usually 20 feet or 6 metres. The alternative number explains the distance at which a person can see a letter clearly.

The ‘E’ that is typically the biggest letter at the top of the chart is equivalent to 20/200. This means you can see from 20 feet what a person with normal visual acuity can see from 200 feet. This measurement means you would be considered legally blind.

Can you have vision better than 20/20?

It is possible to have vision that is clearer than 20/20, but it’s not very common. Young, healthy eyes may have a better chance of seeing the smaller lines of letters and could achieve a measurement of 20/15. This is equivalent to 6/5 in the UK and Ireland.

If you can only see the lines that are slightly larger, you will likely have a visual acuity measurement of between 20/25 and 20/40. The legal driving standard for vision is 20/40, which includes when you are wearing your lenses.

Your eye examination

It’s important to remember that your eye examination is about more than just your visual acuity. Your optician can measure your contrast sensitivity and colour vision, as well as checking your depth perception, peripheral vision and ability to track moving objects.

Your optician will also check your eye health and look for any changes in the anatomy of your eye, which is very important as you may not always notice any changes in your eye health. Many of the common eye conditions don’t present symptoms until much later, when it could be more difficult to treat.

optician during the eye test


Book a regular eye examination with your local optician to make sure your vision is accurately tested and that your eye health is in good condition.

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