3 Visual impairments

3.4 Requirements of people with visual impairments

Here we will focus on the requirements of blind and partially sighted people, differentiating between computers and other interactive products. This differentiation is necessary because with a computer, a person with a visual impairment may have assistive technology installed or connected. This technology is likely to be customised to the user's own circumstances. With an interactive product, assistive technology is less common, and in any case, the product may be a public service device, such as a ticket machine, which a visually impaired person needs to use without bringing their assistive technology with them.

Again, I emphasise that there is great variety in any sort of disability. However, there are some generic requirements that most people in a particular disability group would have in common, and it is these generic requirements on which we focus.

3.4.1 Blind people interacting with computers

The following activity, which you may find rather hard, is designed to encourage you to think about the issues.

Activity 13

Suggest four requirements that a computer application should meet in order to enable blind people to interact with it.


I think the four main requirements are:

  1. The application should be fully operable by means of the keyboard, as a blind user cannot see the effects of moving a mouse.
  2. The application should be compatible with screen readers.
  3. It should be possible to read interface objects and other content with a screen reader.
  4. Interface objects and other content should be able to be read by a screen reader in a way which makes sense to the listener.

In practice, meeting requirement 1 means supporting the standard keyboard shortcuts available for the operating system, such as using the key combination Alt + F4 to close a window of a Windows application, and F1 to open the Help file. It may also be useful to provide special shortcuts for the application, such as the space bar to toggle the ‘play’ and ‘pause’ buttons of a media player.

Typing IDE + accessibility into my favourite search engine in December 2004 gave me information on accessibility and Microsoft Development environments, Java Beans, etc.

Regarding requirement 2, particular development environments might have guidelines or information on how applications developed using that environment can interface with a screen reader. Incidentally, such environments might also have guidelines on how to make the application generally more accessible.

Meeting requirement 3 means that text labels should be provided on all buttons, menus and menu items, icons, sliders, and all other interface objects. Visual objects which convey information as opposed to being simply decorative, should be accompanied by a textual description.

For a screen reader to be able to read a screen in a way which makes sense to a listener, as in requirement 4, the interface objects should be grouped in a coherent and logical way, and this grouping should be consistent across different screens. Of course, having interface objects grouped in logical and consistent ways helps all users – and not just those with visual impairments – to perceive the information on a screen.

3.4.2 Blind people and interactive devices other than computers

Obviously, blind people can't read visual labels, and hence can't use touch-screens, and also can't use pointing devices such as joysticks. One option used on many public service devices, such as banks’ ATMs (automated teller machines) is to provide Braille labels on or next to the buttons. Most blind people learn to read small amounts of Braille and may have sufficient knowledge to read these labels. However, as described above, not all blind people read Braille fluently and therefore it should not be used for large amounts of information. A key point addressed by Braille labels is that blind people need to be able to learn the options available, but without operating them. For example, a ticket machine will have a large number of buttons for different functions, including a ‘cancel’ button. A blind person needs to be aware that a cancel button is available, but for obvious reasons should not need to press it in order to find out its function.

In order to make an interactive device accessible to blind people, output should not be purely visual: audio alternatives should be possible.

The following box describes a commercial software product, available at the time of writing, which improves the accessibility of a mobile phone for people with visual impairments.

Box 3: Making a mobile phone accessible

An example of the provision of speech output from a mainstream device is the TALKS software for a Nokia mobile phone or personal digital assistant (PDA). This software behaves in the same way as screen reader software does on a computer: it reads the content of the screen in synthesised speech, and echoes back the names of keys as they are pressed. This provides access for blind people to text messaging, a calendar, list of missed calls and other functions that were not previously accessible on this phone.

The publicity material (at Cingular) says:

The software itself is stored on a Multi Media Card (MMC) that is inserted in the phone similar to the insertion of a SIM card. Once inserted, this software runs in the background and translates screens, keystrokes, menu selections, etc. into speech output that is audible via the handset speaker or a connected headset, thereby making most phone functions accessible for customers with visual disabilities. This software can tell you if email or text messages have arrived, what calls you've missed and most other key screen functions – all things that before now were only accessibility ‘wish list’ items.

The publicity includes the following:

if you currently use a screen reader, consider yourself somewhat technically savvy, and are willing to undertake the usual new technology learning curve, this product may be exactly what you need to harness the full potential of your phone.

Reading between the lines, this may be seen as a caveat that the software is not suitable for everyone: you might infer that if you don't currently use a screen reader and/or are not technically savvy and/or are not prepared to put in some time learning how to use the software, then this is not for you.

3.4.3 Partially sighted people interacting with computers

The requirements of partially sighted people will vary depending on the individual person's needs and abilities.

3.4.4 Partially sighted people interacting with other interactive devices

Partially sighted people can access the audio output of a device or system, whether this be the voice of a caller on a mobile phone, a pre-recorded information message, or music played on a CD player. However, they may have difficulty accessing a text message displayed on the screen of a mobile phone, or the name of the radio station displayed on a digital radio, or the instructions on a ticket machine.

Activity 14

Suggest some requirements for partially-sighted people using interactive devices. You may find it helpful to review the requirements discussed above for blind users, and consider the comments I have already made about partially-sighted users and the kinds of difficulties they face.


Partially sighted people may need the display of information to be of high contrast and large print, or may need to be able to customise the display to suit their needs. So requirements include:

  • large fonts (or ability to increase font size)
  • high contrast (or ability to change colours)
  • high-visibility controls
  • alternative access to output from the system (possible implementation: speech or audio output).

3.4.5 Colour-blindness

Activity 15

You should allow 0 hour(s), 15 minute(s).

Suggest a requirement for people with colour-blindness using any interactive device.


Colour cannot be used as the only source of information. As an illustration, given the following example found on a university website, how would a person with red-green colour-blindness know when faculty holidays are?

An image showing a text only webpage which uses red and green text on a white background to differentiate types of information

Figure 7: A text only webpage.

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