simulating visual impairments

simulating visual impairments

From the WebAIM website run the simulation that demonstrates how a web page looks to people with a range of visual impairments (macular degeneration, cataract, glaucoma) and the effects of screen magnification.

The simulation requires the Shockwave plug-in that was also used in Activity 3. If you do not have this plug-in on your computer the website will prompt you to install it. Altenatively, you may wish to download and install it now from shockwave/ download/.

First read the instructions, and then start the simulation. Try out some of the different settings under ‘Vision type’, and change the ‘Zoom’ settings. Try some of the activities that appear under ‘Task’.


The Royal National Institute for Deaf People (RNID) estimate that there are approximately 9 million deaf and hard of hearing people in the UK (approximately 698,000 of these are severely or profoundly deaf) and this number is rising as the number of people over 60 increases. The RNID also states that approximately 450,000 severely or profoundly deaf people cannot hear well enough to use a voice telephone, even when using equipment to amplify the sound (RNID, 2005, ‘Facts and figures about deafness’).

When discussing deafness it is important to distinguish between people with severe (or profound) deafness and people who are hard of hearing. Profoundly deaf people do not generally use hearing aids as they provide no benefit. Some hard of hearing people use hearing aids to reduce the effects of the impairment. Hearing aids can allow people to access sound, but the sound is unlikely to be of the same quality as can be heard with unimpaired hearing.

Some deaf people use Sign Language as their primary, or only, language and may not read or write English (or other spoken languages). Sign languages differ from country to country, even those that use the same spoken language; for example British Sign Language (BSL) is different from American Sign Language (ASL).


There are about 23,000 deafblind people in the UK. Some are totally deaf and totally blind, while others have some hearing and/or some vision (RNID, 2005, ‘Deafblind people’). Those who are totally blind may read Braille. Totally deafblind people may use the deafblind manual alphabet to communicate if they cannot hear or speak and cannot see sufficiently to use full sign language. The deafblind alphabet allows the ‘speaker’ to spell out words on the ‘listener's’ hand using specific movements.

Use of computers by deaf or hard of hearing people

In general, people who are deaf or hard of hearing do not require any specific assistive technology in order to use a computer effectively.

  • Deaf people can access visual output and can use a mouse.

  • Hearing aid users may connect their aid to the computer's speakers or an amplifier in order to hear audio output better.

  • Severely deaf people may change the computer's settings so that it provides alternatives to audio alerts etc. by using screen flashes.

  • People who have both visual and hearing impairments may use a refreshable Braille display or other Braille-based devices with a standard keyboard for input.

Physical impairments

People may have a range of physical impairments caused by a wide variety of conditions. It is not necessary to discuss causes of these conditions, but it is useful to note the kind of impairments that people experience. For example, people may have:

  • tremor or shaking

  • weakness

  • pain

  • reduced control of limbs

  • inability to sit upright

  • short or missing limbs.

Physically impaired people may use mobility aids such as wheelchairs or crutches. They may have assistance from other people in daily life and may use a range of assistive devices to control the environment, to manipulate objects or carry out tasks.

Use of computers by physically impaired people

As described above, people may have a wide range of physical impairments, which differ in terms of the extent to which they impair computer use, indeed they may only need suitable furniture. The assistive technology used depends on the person's specific disability.

People who have limited use of their hands or arms, or have reduced control of fine movements, may use a variety of input devices that suit their specific requirements, such as adapted keyboards, mice, trackballs and joysticks etc. The range of pointing devices includes:

  • joystick (like those used for computer games)

  • trackball (like an upside down mouse)

  • touch pad (like those found on some laptop computers).

The range of keyboards includes:

  • single-handed keyboard (left- or right-handed)

  • differently shaped keyboard (e.g. curved shape)

  • different sized keyboards (large with large keys, or compact)

  • on-screen keyboard (operated via a switch, perhaps operated by a single movement).

Physically impaired people may also use operating system utilities to support their use of the keyboard. For example, Microsoft Sticky Keys utility supports users who cannot hold down one key while pressing another by allowing these keys to be pressed in succession rather than in parallel (so to type a capital letter the user can press shift and then the letter).

People who do not have arms or hands, or who cannot use their hands and/or arms, may use an intermediary device to operate a standard keyboard, such as a stick held in their mouth or attached to their head. People with physical disabilities can use a computer as long as they have control over at least one muscle in their body. There are assistive technologies that can translate any controlled movement (however fine or coarse) into computer input, either to select choices or enter text. This might be used to operate on-screen keyboard emulation software.

In addition, this group may also use voice recognition software both for text-entry and for controlling the computer. This type of software has certain functions that allow the user to issue spoken commands to perform mouse clicks. For example, the user could say the phrase ‘click play’ to operate the play button of a media player.

Of course, some physically impaired people may use a combination of different software and devices, such as a joystick instead of a mouse, for clicking and selecting, plus voice recognition software instead of a keyboard to enter text.

Wheelchair users may not have any problems with using a standard keyboard and mouse. The main access issue for this group is whether the computer desk is of a height that will accommodate the wheelchair and allow the person to get close enough to the desk to reach the keyboard and mouse. Wheelchairs vary in height, and people vary in height and reach; therefore height-adjustable desks are available that can adapt to suit different wheelchair users and their wheelchairs.