3 Visual impairments
3.3 Assistive technologies for the blind and partially sighted
Most of this section is concerned with discussing assistive technologies to help firstly blind and then partially sighted people to perceive the output of a computer – obviously, blind people can't see screens and partially sighted people might find it difficult. We will then discuss how visually impaired people can input data to a computer.
3.3.1 Assisting the perception of computer output by blind people
Blind people access computer output using a combination of software and hardware that present the visual contents of the screen in another form, either in synthesised speech, or in Braille.
Screen readers and speech synthesisers
A screen reader monitors the information sent from the computer to the screen. It passes this information to either a speech synthesiser or a Braille display. All screen readers support speech synthesisers, and most support Braille displays.
Speech synthesisers may consist of a small box that sits on the desktop and has its own speaker, or may be a card that fits inside the computer and uses external speakers or those of the computer. The main advantage of using a speech synthesiser with a screen reader over a Braille display is that synthesisers are cheap, and often come as standard with new computers, as we will see later in Activity 12.
As well as presenting the information on the screen, screen readers also provide additional functionality to allow the user to interact with the information. For example, screen readers may have commands for pausing or repeating the speech, and echoing back keyboard input. The user may be able to control the amount of information that is read, for example a paragraph, a line, a word, or a character at a time. The user can also move the focus backwards and forwards in the text, may also be able to control the rate and pitch of the speech, and to choose between different voices.
There are several difficulties associated with using a screen reader and speech synthesiser to access a computer. The main one is that it is very difficult to obtain a quick overview of the information on the screen because it is presented in a ‘linear’ manner, i.e. the contents of the screen are read out word by word, and there is no equivalent of the visual glance. This linear approach also means that it takes much longer to read a screen-full of text using synthesised speech. In addition synthesised speech can be very tiring to listen to over a long period of time, more so than human speech.
The next activity illustrates the use of a screen reader with a speech synthesiser.
You should allow 0 hour(s), 30 minute(s).
For this activity you will need the ActiveX control: Shockwave player 10.1 from Adobe Systems incorporated. Extensive audio content needs to be downloaded and this may take several minutes to download.
Screen Reader Simulation
Click here to run the Screen Reader Simulation. This contains a screen reader simulation and a screen reader sample website (University of the Antarctic). The simulation is designed to illustrate a screen reader reading this website. I suggest that you initially have only the screen reader open, and shut your eyes. This will illustrate for you what it may be like to have only the information from the screen reader available to understand the website. The simulation suggests three activities for you to perform using the screen reader. I suggest that you try task 2, to find the phone number for the university.
After you have found the phone number (if you can), or after trying this for 5 minutes, open the website for the University of the Antarctic as well as the screen reader simulation so that you can compare the screen reader output with the visual website.
What kind of difficulties did you encounter?
I found that identifying the phone number was very difficult using only the screen reader. In fact, I didn't manage to finish this task. One of the difficulties I had was in understanding the reader's speech which I found not very clear. Secondly, because the screen reader needs to include every element of the screen, not just menu options or screen text, I found it very distracting to filter out the formatting elements. Thirdly, the screen reader did not read out the headings on the ‘contact us’ page, and so I had to be quick to recognise that the phone number was being read.
Having spent some time using a simulation of a screen reader with a speech synthesiser, what implications do you think this has for interaction designers?
If interaction designers are going to design applications to be accessible to blind people, then it is important to take screen reader facilities and limitations into account.
Braille displays are also driven by screen reader software. Such displays are used in conjunction with the keyboard provided with the computer so that the user can easily access both, see Figures 2 and 3 below. There are models to suit both laptop and desktop machines.
A Braille display has a number of Braille cells (usually 20, 40 or 80) in a row. These cells are groups of 6 or 8 plastic pins arranged in a matrix. The cells are ‘refreshable’ which means that the pins can move up and down to create Braille characters. The row of cells displays one line, or part of a line, of the text on the screen. As the user moves the cursor up and down the screen, the Braille display presents the rows of text.
Figure 2: A Braille display with a standard keyboardView description
Figure 3: Using a Braille displayView description
Perhaps obviously, the use of a Braille display requires the user to be able to read Braille. Contrary to popular belief, only a small percentage of blind people can read Braille proficiently. A survey conducted by the Royal National Institute for the Blind found that only 3 per cent of visually impaired people are sufficiently fluent in Braille to read a book or magazine (Bruce et al., 1991). The majority of blind people lose their sight later in life, either progressively, or through an accident, and therefore do not learn to read Braille as a child. Most blind people who have lost their sight later in life do learn to read Braille, but do not usually reach a stage at which they can read it efficiently enough to use a Braille display with a computer.
There are several advantages of using a Braille display with a screen reader over a speech synthesiser. Users can read as fast as they like and are not restricted by the rate of the synthesised speech. Also the user gets a better idea of the spatial layout of items on the screen. The main disadvantage is that Braille displays are very expensive (for example in 2004 prices in the UK started at around £3,500). They are therefore mainly used in the workplace where they may be purchased with government grants.
3.3.2 Assisting the perception of computer output by partially sighted people
Partial sight is caused by a range of eye conditions, which affect vision in different ways. This means that partially sighted people have a range of different needs for accessing the output of a computer.
Partially sighted people may require particular computer display settings to optimise their ability to see the screen. For example, some people find that particular colour combinations for text and background are easier to see. A common preferred combination is yellow text on a black background. Some people may prefer certain font styles, such as sans serif fonts, or may need larger font sizes in order to read text. Such people may change the default font or increase the font size via operating system settings. A serif is a short line at the end of the main stroke of a character. is an example of a font with serifs (see those little twiddles on the N!); Helvetica is an example of a font without serifs (a sans serif font).
The effects of changing colours and font sizes is seen in Figure 4, showing the home page of AbilityNet with default and high-visibility (Hi Viz) settings as offered by the website. You may also be able to change font sizes and colours by means of the operating system or web browser settings.
Figure 4: (a) AbilityNet home page with default settings. (b) The same page with the Hi Viz settings (http://www.abilitynet.org.uk/content/home.htm)View description
Some people who require large fonts, or who need to enlarge pictures or icons, may use a software magnifier. A basic magnifier is available within operating systems, such as Windows and Mac OS, as we will see later in Activity 12. More sophisticated software magnifiers are also available which provide additional functionality, such as the following:
- magnification of the whole screen
- magnification of area around the mouse cursor (like an on-screen magnifying glass)
- magnification of half of the screen (vertical or horizontal split)
- colour settings applied to everything on screen
- speech output.
Partially sighted people may use a combination of magnification, colour and speech, depending on their particular circumstances or the task they are performing. The effect of using screen magnification software, in this case, ZoomText version 8.1 from Ai Squared is shown in Figures 5a–d on the following pages.
Figure 5: (a) The Open University home page as it appeared in November 2004, without magnification. Note that the whole screen can be viewed at once by a person without a visual impairment. (b) Example of a ’lens’ magnification facility in which the magnified area (the black box) acts as a magnifying glass, magnifying everything under it as the mouse cursor is moved around. The magnified area moves with the mouse cursor.View description
Figure 5: (c) Example of a ‘line’ magnification facility in which a horizontal area around the mouse cursor is magnified, as if line by line. The magnified area moves with the mouse cursor, (d) Example of the half-screen magnification facility. The left-hand side of the screen shows the non-magnified image and the right-hand side shows the magnified image of the area around the mouse cursor.View description
Of course, when the screen, or a portion of the screen, is magnified, a smaller proportion of the screen can be seen at one time. This will have an impact on tasks that require the user to monitor or look at different parts of the screen at the same time. For example, a user with unimpaired sight who is loading a web page can easily glance at the browser status bar to monitor the loading progress. In contrast, a user who is using a screen magnifier will have to move the magnified area to the status bar to monitor it, and then return it to the top of the page to start reading.
As mentioned above, screen magnifying software can provide speech output to the user. This can help to overcome the difficulty described above of needing to look at, or monitor, different parts of the screen.
You should allow 0 hour(s), 30 minute(s).
Software to support accessibility
Microsoft Windows includes some facilities to support accessibility for partially sighted users. From the Start menu, find Programs and Accessories and then the Accessibility menu item. This includes a magnifier, a narrator and an on-screen keyboard.
Turn on the magnifier and then access a text document, a document containing some graphical images, and then a website. What difficulties did you experience?
Now turn off the magnifier and turn on the narrator. This has quite limited functionality compared with the screen reader simulation in Activity 10, but it does provide some accessibility support, and is intended for partially-sighted users, not blind users.
The magnifier provides a larger view of the screen, but the characters become difficult to understand at the higher magnification levels because they lose their coherence and begin to look just like blocks of colour piled together. It can also be difficult to follow where on the screen you are, as you have to balance the size of the magnified screen image with the overview of the screen.
The narrator is very limited, but it tells the user which window is active and which menu item is being scanned. For partially-sighted users, this can be sufficient to confirm that they are choosing the right operation.
3.3.3 Assisting computer input by blind and partially sighted people
Blind people cannot use a mouse to input to the computer because this requires hand-eye coordination, and so they rely on the keyboard for input of text, and to operate applications and the operating system. For example, it is possible to use most Microsoft applications under the Windows platform without using the mouse at all and just using the available keyboard shortcuts. The Help file of Microsoft applications and the Windows Help file provide lists of available keyboard shortcuts.
Partially sighted people can learn to touch type as sighted people do, however this can be a difficult process if you cannot see the screen or the keyboard clearly. A simple, low-tech solution to make the keyboard more visible is the use of large print labels which can be attached to the keys. Alternatively, a high-contrast keyboard can be used, for example a black keyboard with black keys with yellow characters. In addition, speech output software can announce every key that is pressed so that the user can receive feedback as they type. Partially sighted people may use a mouse as well as the keyboard, depending on their level of vision.
Figure 6 shows an example of a commercially available keyboard (as of 2004) aimed at partially sighted people (and also at people with some motor impairments). Compared to standard keyboards, this keyboard has a reduced number of large colourful keys.