Visual acuity and 6/6 vision
Visual acuity is a measure of your central vision, the ability to distinguish details and shapes of objects.
Distant vision is tested with a chart with differently sized letters read from a distance of six metres away. This is called the Snellen’s Test Types.
Someone who can read the second line of letters up from the bottom is said to have 6/6 vision. This used to be called 20/20 vision when the test was done from 20 feet away before metric measures took over.
6/6 does not translate into perfect vision and does not indicate other important aspects of sight such as peripheral vision, the ability to identify colours or depth perception.
Having 6/12 vision means you can see at six metres what a person with normal vision can see at 12 metres away.
Each eye is tested separately - and an overall score is given for both eyes or binocular vision. So a person's Snellen test scores might be: