What do we mean by 'vision impaired' ?

There are various definitions which describe this disability, but in simple terms it could be:

  • Partially sighted - a person can see but with some difficulty;

  • Low vision - a more severe impairment of vision, but not necessarily limited to distance vision. This would be someone with sight
    who is unable to read a newspaper at a normal viewing distance, even with the aid of eyeglasses or contact lenses;

  • Blind - a person having no useful sight.

How the vision impaired use a computer

Office for employees who are blind (US video)

How does someone with a vision impairment use a computer ?

Dependent on the severity of the impairment, there are a number of products available or computer adjustments that can be made, which allow you to use a computer more easily.

Those with partial or low vision:

Those with no useful sight:

Other visual difficulties:

  • Light sensitivity. Some people are affected by the light emitted by the computer monitor. Sometimes this can be resolved by either increasing or decreasing the monitor refresh rate. CRT are generally worse than LCD (flat screen). Other ways of reducing these affects include using Coloured screen overlays or Anti-glare filters. There are varying degrees of filtering available. The filters reduce the strain on the eyes by blocking 99% of ultraviolet rays radiated from LCD screens. In addition, the filters allow 90% of light transmission while protecting the LCD screen from degradation as a result of strong sunlight and other natural lights.

    What the RNIB say about light sensitivity (photophobia)

    Anti-Glare Filters:

    filter image
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    LCD screen filter




  • Photosensitive Epilepsy. The name given to epilepsy in which all, or almost all, seizures are provoked by flashing or flickering light, or some shapes or patterns. Both natural and artificial light may trigger seizures. Various types of seizure may be triggered by flickering light. The word hertz (Hz) refers to how often something happens in a given time. In photosensitive epilepsy, hertz (Hz) refers to the number of flashes or flickers a second. When talking about televisions or computer screens, hertz refers to the rate the scanning lines ‘refresh’ themselves. Most people with photosensitive epilepsy are sensitive to 16-25 Hz, although some people may be sensitive to rates as low as 3 Hz and as high as 60 Hz. Anti-glare screens do not reduce the flicker rate and are therefore of no specific benefit to people with photosensitive epilepsy.

    Photosenstive Epilepsy and computers (Source:

    Many people think that people with photosensitive epilepsy are not able to use computers, because they will trigger a seizure. Although some images being displayed on the screen could be a problem, using a computer in itself is extremely unlikely to trigger a seizure. LCD or TFT screens are thin, flat, screens which are flicker free. This means they are unlikely to trigger seizures..

    More useful advice (Source: National Society for Epilepsy) . . .

    Some useful tips for light sensitivity issues (Source:

    • Changing Background Colors
      Eyestrain and flicker can also be reduced by changing the background colors of your computer applications from the color white, to a darker color, and making the text brighter if necessary.
    • Contrast and Brightness
      If you are light sensitive, try setting the brightness and contrast as low as possible. If the lowest settings are too dark, adjust the contrast before adjusting the brightness. Adjusting the contrast is preferable to increasing the brightness. Contrast is the degree of difference between the lightest and darkest parts of a picture.
    • Adjusting LCD and CRT Monitors
      For good LCD viewing, set brightness so that whites are displayed at a comfortable intensity. Then, set contrast so that blacks and whites are as distinct as possible - that is, so the displayed contrast ratio is sufficiently high.
      Reducing eyestrain from video and computer monitors

  • Cerium OverlaysVisual Stress. Many children and adults suffer from visual discomfort when reading. This can affect reading fluency, concentration and comprehension and can cause rapid fatigue. This Visual Stress can cause symptoms such as movement of print, rivers running through the print and headaches/eyestrain. It's said to exist in many conditions, including: Dyslexia, Dyspraxia, Photosensitive Migraine, Photosensitive Epilepsy, Autism and ADHD. Visual stress is defined as a condition which is also known as “Mears-Irlen” syndrome. It refers to reading difficulties, light sensitivity and headaches from exposure to disturbing visual patterns. It can be responsible for print distortion and rapid fatigue when reading. The severity of these symptoms can vary from person to person. Coloured overlays can enable an increase in reading fluency, efficiency and duration. (Source:Cerium Optical).

  • Irlen syndrome - Irlen Filters. People with Irlen syndrome or Scotopic Sensitivity Syndrome cannot read comfortably. The words are not clear and easy to see. There is no typical Irlen syndrome profile. The symptoms vary from person to person and there are many variables involved such as:
    • Light Sensitivity - fluorescent, sunlight, car headlights.
    • Contrast – reading black print on white paper.
    • Print – words blurring, or merging together.
    • Span - Unable to see groups of letters or words clearly at the same time.
    • Concentration - Problems concentrating on reading or writing.
    • Depth - Inability to judge distance and spatial relationships accurately. May bump into things, have difficulty with ball games and stairs.

    Coloured or tinted filters called Irlen filters can be prescribed that helps an individual overcome the debilitating effects of the condition. The assessment involves an intensive diagnostic process. More information about Irlen Syndrome . . .

  • Computer glare and software overlays (courtesy of Chris Stringfellow at AbilityNet).

    Dark Screen. Some computer users experience problems with glare from the screen. Dark Screen sits over all windows and provides a means of dimming the output between 20 and 90%. Dark Screen is multi monitor aware, and can be used on the main monitor only or all monitors. Everything is controlled from the icon in the Notification area of the Taskbar (where the clock sits). Clicking this icon will open the menu which allows the selection of Multi Monitor Support, and the percentage of dimming of the screen.

    Screenshot of Dark Screen

    Download Dark Screen . . .

    SSOverlay. Very similar to Dark Screen, ssOverlay (the ss stands for Scotopic Sensitivity), places a coloured overlay onto the screen. The colour and transparency levels can be adjusted to suit the user.

    Screenshot of ssOverlay

    Download ssOverlay . . .

  • EyePilot logoColour blindness or Colour blindness , a colour vision deficiency, is the inability to perceive differences between some of thecolours that others can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve or brain damage, or due to exposure to certain chemicals. (Source: Wikipedia).

    ColorHelper has developed interactive software called EyePilot which allows colour-blind people to work more efficiently with the full range of colours in the computer environment. This application is designed as an interactive floating window which can be used to layer over any browser window on your computer screen. The eyePilot tools will then start to work. When you click upon a particular element on the screen, the rest of the screen will turn gray. This allows you to see better the colour of your choice. A second click will cancel the effect. (Source: MyDigitalLife). See more information about EyePilot, by ColorHelper . . .

    New Product - Huetility ColourBlindness Simulator App for the iPhone

    The Huetility Colourblind Simulator app is intended for people who know someone who is colourblind and want to better understand how he or she perceives colour. It's ideal for parents with children who are colourblind or people who have friends who are colourblind. It's also useful for designers, content creators and developers who want to check that colours they have used are colourblind friendly.

    The Huetility app has three important views: 1) normal colour vision, 2) colourblind view (including severe red-green, blue-yellow and complete colour loss) and 3) an error view which highlights, using a grayscale intensity image, the regions of the colour image that change colour the most and hence are likely to cause a colourblind viewer the greatest problems.

    Vision - Global Assistive Technology WikiScreenshot of the Huetility app for the iPhoneScreenshot of the Huetility app for the iPhone

    The images can be loaded directly from the camera, your photo album or from the samples folder included in the application; the samples folder contains 28 images selected to highlight the accessibility barriers colourblindness presents.

    More information about this colourblindness app at:

Screen Tinter
Some individuals with apparently normal eyes, experience discomfort and eye strain when viewing computer screens. In some cases these symptoms can be relieved by changing the screen colours. This can be achieved by changing the Windows Display Properties. However, this process is cumbersome and counter-intuitive. Screen Tinter is a free utility which allows the screen foreground and background colours to be changed at the click of a button.

Screenshot of Screen Tinter
Simply select your preferred Background and Text colour from the palette of the Colour Picker control and click on Set Screen to this Colour and magically all Windows applications will adopt your chosen colours. Click on Reset screen to white to return to the default settings.

More useful information about Screen Tinter Lite at Charlie Danger's BLTT website

This is a useful guide for changing colours in Internet Explorer:

T3 Tactile Talking Technology

The T3 is a touch sensitive, multi sensory device which provides instant audio feedback from tactile images. This combination of sound and touch transforms the way in which people who are visually impaired can access graphical information. The T3 is connected to a standard PC or laptop computer via a USB connection and the self-installing programme CD is inserted. To activate the system all that is needed is a T3 tactile diagram overlay to be placed on the surface of the device and touched by the operators finger. (Source: Royal National College for the Blind)

The tablet consists of a touch screen within a plastic surround which houses the tactile embossed sheets with maps, images etc. When various symbols, icons, and regions on the tactile surface are pressed, an audio response comes from a connected computer. The types of voice output depends on the speech synthesis available. PC based software is provided to allow for the design of maps etc and these can be adapted to suit learning preferences. (Source:

T3 Tactile Talking Technology screenshot

Image of T3 tactile tablet

Image of talking tactile tablet

Screen reading software

Products in practice

This is a novel way to use a Fresnel lens !

Using the free screenreader called Thunder.

Using AT - overcoming Low/No vision difficulties.

Using a screen magnifier - in this example, 'ZoomText'.

Lormer - Computer technology for the DeafBlind

The Lormer is a machine invented by Thomas Rupp which translates machine text into movement. It assigns a defined meaning to particular motion - a letter or a sign - and reproduces it. This movement is then applied by a stylus in Lormen lines to a hand resting on a comfortable metal grid (like a kitchen sieve). The Lormer registers and stores three dimensional motion. Each motion can be tuned or set individually and matched to the size of any hand, and can be stored and retrieved.

Using the Lormer deafblind people can read and access machine readable text without external assistance or translation and can therefore communicate directly with others.

Watch a youtube video of the Lormer and how it was developed . . .

Screenshot of the Lormer device for the deafblind

iRotate (free software)

iRotate provides convenient access to the native rotation capabilities present in contemporary display drivers, via a popup menu accessible from the system tray and optional system-wide hotkeys. It's no longer necessary to resort to additional software layers or phantom drivers to achieve content rotation. In most instances, support is now available directly from the graphics chip manufacturers, who continuously improve and apply quality assurance to their drivers.

By usiing the native rotation capabilities now provided by ATI, nVidia, Intel, Matrox, S3, XGI and others, iRotate offers speed and efficiency, with minimal impact on scarce system resources. iRotate supports multiple graphics cards from various vendors, simultaneously, under every multi-monitor enabled operating system from Windows 98 to Vista.

Link to download iRotate . . .
Screenshot of iRotate software

Useful Resources

Vision Technology Suppliers

Free software