Have you ever wondered what exactly is vision impairment? Maybe you’d like to know the difference between being totally blind or legally blind. And what is 20-20 vision?
If you or someone you care about is diagnosed with blindness or vision impairment, all of these terms can be daunting. Here we explain some key terminology to help you through.
Vision Impairment: A vision impairment is technically defined as a limitation of one or more function of the eye, or visual system.
This means, a person with vision impairment, or low vision, does have some useful vision, however their vision loss is severe enough to affect their everyday life. This can include affecting a person’s ability to perform vocational, recreational and/or social tasks. Low vision can’t usually be corrected to normal vision with regular glasses.
Totally Blind: a person who is considered totally blind has no measureable or useable vision, and no light perception.
Legally Blind: is a term used by the 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.
The term 20/20 vision relates to the same acuity measurement as 6/6, but it is reflected in feet rather than metres. In Australia, where we use metric measurement, 6/6 is a more accurate term to use.
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, compared to the normal field of vision of 180 degrees, or a combination of both reduced visual acuity and field of vision.
Find out more
If you have concerns about your vision, or to find out more about financial entitlements for people who are legally blind, contact us today.