Most of us have heard of the expression ’20/20 vision’ but what does it actually mean?

20/20 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance. If you have 20/36 vision, it means that you must be as close as 20 feet to see what a person with normal vision can see at 36 feet. And if you have 20/16 vision, you can see at 20 feet what a person with normal vision can only see at 16 feet.

How is visual Acuity Measured?

The Snellen Chart

This visual acuity is measured by your ability to read letters or numbers on an eye chart.  The most commonly used chart is the Snellen chart, named after Herman Snellen, the Dutch ophthalmologist who developed this eyesight measurement system in 1862.

So what is 6/6 Vision?

The distance used for measuring visual acuity was historically 20 feet but as the UK now uses the metric measurement of 6 metres, we should now really refer to 6/6 eyesight.

Is 20/20 vision perfect?

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 of 20 feet. Other important vision skills, including peripheral, or side vision, eye coordination, depth perception, focusing ability and colour vision, contribute to your overall visual ability.

Some people can see well at a distance but are unable to focus on near objects. This condition can be caused by hyperopia (farsightedness) or presbyopia (loss of focusing ability). Others can see items that are close but cannot see those far away. This condition may be caused by myopia (nearsightedness).


Eye Examinations

To see as clearly and comfortably as possible, it is important to attend regular eye examinations.  Your optometrist can prescribe glasses or contact lenses, and where necessary, refer for further treatment or investigation.  If you are over 60 the cost of the examination is covered by the NHS.  The Richard Tildesley Practice Chichester welcomes private and NHS patients and will provide a comprehensive examination.  To find out more about the services we provide, go to The Richard Tildesley Practice .  For our most thorough examination, you can also have an OCT retinal scan – see more about this at OCT Retinal Scans



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