Terms used when talking about different levels of sight loss.
Visual acuity is a term used to describe the sharpness of the images seen. It is generally measured by a Snellen Chart which has nine rows of letters in decreasing sizes. Perfect vision can be expressed as a group of numbers i.e. 20/20, which means an individual can see the same detail at 20 feet as a standard observer can.
How bad does your visual impairment need to be to be registered as a blind or partially sighted person?
The definition of blindness used in registration is still taken from the National Assistance Act 1948, which states that a person can be certified as blind if they are ‘so blind that they cannot do any work for which eyesight is essential’.