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:
  
  

  (Image: Screenfilter.net)

  (Image: Screenfilter.net)

  (Image: Screenfilter.net)

  (Image: LaOffice.co.uk)

  
  Suppliers:
  
  Screenfilter.net
  
  ComputingPlus
  
  3M
  
  
  
• 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.
  (Source: Epilepsy.org)
  
  Some useful tips for light sensitivity issues (Source: Prodigy.net)
  
  
  • 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
    
    
• Visual 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. 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. Download ssOverlay . . .

  
  
  
• Colour 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. When you rotate the device (left) it shows you the comparison of the original and simulated colourblind viewers. When you rotate the device (right) it shows you a view of all the different types of colourblindness for the loaded image. Other options include: save image, view image histogram.
  
  

  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.
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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 . . .

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 . . .

Useful Resources

Vision Technology Suppliers

• Vision Enhancers
• ForceTenCo
• Blazie
• VisualEyes
• Professional Vision Services
  

Free software

• iZoom Free web-based magnification and screenreader program. Requires connection to the internet.
  
  A good review of iZoom: http://magnifiers.org/popularnews.php?action=fullnews&id=284