There are many different types of vision loss, ranging from mild vision impairment to total blindness. Blindness and vision loss can be caused by a number of conditions and diseases, as well as accidents.
A person with vision impairment or low vision does have some useful vision, however their vision loss is severe enough to affect their ability to perform vocational, recreational and/or social tasks. Low vision can’t usually be corrected to normal vision by regular glasses.
A person who is totally blind has no measurable or useable vision, and no light perception.
Legally blind is a term used by government to identify people who are eligible for special benefits and services.
How is Vision Impairment Measured?
Visual acuity is a measure of what the eye is able to see at a set distance of 6 metres for distance vision and 33 centimetres for near vision. Vision is tested one eye at a time using a standard letter chart.
Visual acuity of 6/6 is regarded as ‘normal vision’. The first number shows the distance of the person from the chart in metres, while the second number shows the measured result. For example, 6/60 means that a person six metres from the chart is seeing what a person with ‘normal vision’ can see at sixty metres.
Visual field includes a person’s peripheral vision in the measurement of their vision. That is, what can be seen all around while looking straight ahead. Visual fields can be measured using standardised tests. Complete loss of peripheral field of vision is often referred to as ‘tunnel vision’.
What level of vision is regarded as legally blind?
A person who cannot see at six metres what a normally sighted person can see at 60 metres, is considered legally blind. A person who is legally blind is someone who has less than 6/60 vision in their better eye or has a field of vision restricted to 20 degrees in diameter or less (a normal field of vision is 180 degrees) or a combination of both (reduced visual acuity and field of vision).