Visual impairment is when a person has sight loss that cannot be corrected using glasses or contact lenses.
There are two main categories of visual impairment:
- being partially sighted or sight impaired – where the level of sight loss is moderate
- severe sight impairment (blindness) – where the level of sight loss is so severe that activities that rely on eyesight become impossible
How vision is measured
There are two main areas that are looked at when someone's vision is measured:
- visual acuity – which is your central vision and is used to look at objects in detail, such as reading a book or watching television
- visual field – which is your ability to see around the edge of your vision while looking straight ahead
The Snellen test
A Snellen test measures your visual acuity. It involves reading letters off a chart on which the letters become progressively smaller. This chart is used during a routine eye test.
After the test you are given a score made up of two numbers. The first number represents how far away from the chart you were able to successfully read the letters on the chart. The second number represents how far away a person with healthy vision should be able to read the chart.
So if you were given a visual acuity score of 6/60, it means you can only read 6 metres away what a person with healthy eyesight can read 60 metres away.
Visual field testing
During visual field testing you will be instructed to look straight ahead at a device while lights are flashed on and off in your peripheral vision. You will be asked to press a button every time you see a light. This shows any gaps in your field of vision.
Partial sight, or sight impairment, is usually defined as:
- having very poor visual acuity (3/60 to 6/60) but having a full field of vision, or
- having a combination of moderate visual acuity (up to 6/24) and a reduced field of vision or having blurriness or cloudiness in your central vision, or
- having relatively good visual acuity (up to 6/18) but a lot of your field of vision is missing
Severe sight impairment (blindness)
The legal definition of severe sight impairment (blindness) is when ‘a person is so blind that they cannot do any work for which eyesight is essential’.
This usually falls into one of three categories:
- having extremely poor visual acuity (less than 3/60) but having a full field of vision
- having poor visual acuity (between 3/60 and 6/60) and a severe reduction in your field of vision
- having average visual acuity (6/60 or better) and an extremely reduced field of vision
There are support services, charities and devices that can all help make life easier if your vision is impaired.
Just because you have low vision, it does not mean you are no longer able to work. With the help of assistive technology, training and support, many people who are either partially sighted or blind can continue to work in often very demanding roles. Probably the most well known example is the politician David Blunkett.
Read more about.
Registering as visually impaired
It is also important that you register as visually impaired. To register, your visual acuity and visual field will have to be tested by an ophthalmologist (a doctor who specialises in treating eye conditions).
If the results show you are partially sighted or blind, you will be issued with what is known as a Certificate of Visual Impairment (CVI) and a copy will also be sent to your local social services.
Being registered as visually impaired can entitle you to a range of benefits, such as:
- Disability Living Allowance (DLA) – a tax-free benefit to help with any costs a person has relating to their disability
- a 50% reduction in the TV licence fee
- tax allowance
- a disabled person’s card
Your doctor or ophthalmologist can provide more information on registration.
Some of the most common causes of visual impairment include:
- (AMD) – where the central part of the back of the eye (the macular, which plays an important role in central vision) stops working properly
- – where cloudy patches can form on the lenses of the eyes
- – where fluid builds up inside the eye, damaging the optic nerve (which relays information from the eye to the brain)
- diabetic retinopathy – where blood vessels that supply the eye become damaged due to a build-up of glucose
Can vision be restored?
It depends on the underlying cause.
Cataracts can be treated with surgery that usually leads to at least a partial improvement in vision. Read more about.
In cases of AMD, glaucoma and diabetic retinopathy, it is usually not possible to restore vision. However, there are several treatments that can prevent further damage to vision, or at least slow down the progression of these conditions.
Read more about treating AMD](/health-library/conditions/macular-degeneration/#treatment),and [treating diabetic retinopathy.
Help and support
Being told you have a visual impairment or you are going to be visually impaired in the future can have a tremendous emotional impact.
Many people have reported going through a process much like bereavement, where they experience the following emotions:
- shock and numbness – ‘it was like I was in a daze and nothing was real’
- anger – ‘I remember thinking “why me, I don’t deserve this”. I was furious’
- denial – ‘I felt sure there was nothing wrong with my eyes and the doctors had made a mistake’
- fear and anxiety – ‘I felt so scared of the future, knowing my sight was going to get worse’
- sadness and grief – ‘I just sat in my room for hours crying and crying’
- acceptance – ‘I started planning how I was going to live with a visual impairment and I started feeling more optimistic about the future’
Most people come to terms with their visual impairment, but in some people the diagnosis can trigger, especially in the first few months.
You may be depressed if during the past month you have been very down and felt hopeless, and you no longer take pleasure in activities you used to enjoy.
If you are concerned that you may be depressed, you should contact your doctor as there are several treatments that are usually effective for most people, such asand . Read more about .
Changes to your home
Most people with a visual impairment can continue to live at home. However, you will probably need to make some changes to your home, especially if you live by yourself.
There are several important pieces of equipment you should consider buying:
- Big-button telephone – both landline and mobile models are available from the RNIB online shop.
- Computer – the internet can provide a real sense of connection to friends and family as well as other people with a visual impairment. It is also a practical way of finding out information and obtaining goods and services. Big-button keyboards, screen display software and text readers are available from the RNIB.
- Community alarm – this small wearable device has an alarm button. If pressed it sends an alarm signal to a response centre, which will alert a nominated friend or carer. Your local authority should be able to provide you with more information.
- Bright lighting – bright light bulbs and adjustable lights are essential for your home, especially in the kitchen and the stairs (areas where you are most likely to have an accident). Fluorescent bulbs are recommended, as these produce the most light and tend to be cheaper in the long term than conventional bulbs.
The way your house is painted can also make it easier to find your way around. Using a two-tone contrast approach, such as black and white, can make it easier to tell the difference between nearby objects, such as a door and its handle or the stairs and its handrail.
Many people who are visually impaired find it useful to use a long cane when travelling.
This is a long, usually foldable cane that can help you get around by detecting objects in your path. It also lets drivers and other pedestrians know that you have a visual impairment.
To get the most use out of a cane, you will need to attend a training course in how to use it.
Global positioning system
A global positioning system (doctorS) is a navigational aid that uses signals from satellites to provide a real-time update on a user’s current geographical location.
doctorSs are available as stand-alone units that can be programmed using a Braille keyboard (see below), which then provides both a visual map and a voice prompt of your current location.
Alternatively, you can download a number of doctorS apps to your smartphone.
However, it is important to note that doctorSs will usually only work if you are outdoors.
The RNIB has more information on how doctorS can help people with visual impairment.
Reading and writing
If you are having problems reading standard texts in books, newspapers and magazines, there are several options available.
E-readers are handheld devices that allow you to download books and subscribe to newspapers and magazines on the internet. You can then set the device to display text at a larger size.
If you are unable to read at all, you could install screen-reading software on your computer that will read out emails, documents and text on the internet.
A charity called Communication for Blind and Disabled People has released a free screen reader for the PC called Thunder. Download the screen reader.
Similar software is available for Apple devices, although you may have to pay a small fee.
There are also voice recognition programmes where you speak into a microphone and the software translates what you say into written language.
You can also use the software to issue commands such as closing browser windows and moving from one website to another.
Some people who are severely sight impaired choose to learn Braille. Braille is a writing system where raised dots are used as a substitute for written letters.
As well as Braille versions of books and magazines, you can buy Braille display units, which can be attached to computers so you can read the text of a computer screen.
Braille keyboards are also available, so you can use Braille as a writing system.
The RNIB has more details about reading and writing and how you can become trained in using Braille.