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Technology for Visually Disabled Persons: The Widening Gap

Dr John Gill
May 1995

In geographic Europe, the estimated number of people with impairments is:


Wheelchair user 2,800,000

Cannot walk without aid 45,000,000


Cannot use fingers 1,100,000

Cannot use one arm 1,100,000

Reduced strength 22,500,000

Reduced co-ordination 11,500,000


Profoundly deaf 1,100,000

Hard of hearing 80,000,000


Blind 1,100,000

Low vision 11,500,000

Speech and language

Speech 2,300,000

Language 5,600,000

Dyslexia 25,000,000

Intellectually impaired 30,000,000

In the UK, Bruce, McKennell & Walker (1991) found that although 148,000 people were registered as blind or partially sighted, there were about 959,000 adults whose vision was such that they could be registered. Of these 959,000, 55% live alone and 35% have a hearing deficit. About 19,000 can read Braille, 13,000 claim that they do read it and only 9,000 can write Braille.

There is an increasing amount of research being done in Europe which has been stimulated by funding from the Commission of the European Union (particularly the TIDE programme).

An example is the distribution of textual information for blind persons in digital form. This involves there being some standards for the data format which must be such that it facilitates easy searching, browsing and reading by a blind person with a variety of output modalities such as Braille or synthetic speech. Structures such as hypertext often require intervention to convert the raw text to an optimal structured file - this adds to the cost. A separate matter is the method of distribution - this could include floppy disc as well as telecommunication links which will come increasingly attractive when ISDN becomes generally available to domestic users.

For many software houses, user-friendly computer systems mean GUIs (graphical user interfaces). In the medium term, new operating systems, such as the next version of X-Windows, will have "hooks" which will assist in the development of adaptations for blind persons. In the long term, the situation appears likely to deteriorate because of the development of "locked" operating systems.

GUIs will be used in other applications than access to conventional computer systems; for instance "smart housing". The area of smart housing for disabled persons is of great interest to the governments of a number of countries. The reason being that they have done a simple calculation of the number of disabled and elderly persons by the turn of the century, and the number of people in work at that time who will be paying taxes. This calculation has led them to conclude that a greater percentage of elderly and disabled persons will have to be able to live independently, and they forsee that the appropriate use of smart housing will make this economically possible. Therefore it is important that the design of the man-machine interfaces for smart housing takes into account the needs of visually disabled persons. For instance it would be technically possible to have a family of controllers designed for the needs of various groups of disabled persons.

One piece of domestic equipment, which cannot be adapted for blind persons just by changing the interface of the controller, is the television set. However audio description of television programmes has proved popular in north America and Japan. The audio description of the action of the programme is inserted in the gaps in the dialogue. The technical problem is that, in Europe, there is not a spare audio channel for transmitting the audio description. Therefore other methods are being investigated, but with the most promising option being to use two lines of the vertical blanking interval. This is another project being funded by Tide since it would require an European market to justify the development cost of the chip to be used in the receivers.

The storage of audio information has long been of importance to blind persons. Problems with conventional compact cassette systems have included controlling the speed of playback and indexing. Compressed (and expanded) speech chips have been around for some years, but relatively few tape recorders include this facility. Although various methods have been devised for indexing, none could be described as being ideal. Therefore the advent of digital storage (eg compact disc) offers exciting possibilities since it is capable of giving excellent audio quality in addition to sophisticated facilities such as compressed speech and indexing. It would also be relatively simple to incorporate circuitry to partly compensate for any hearing loss of the user. However there is a significant problem in that CD type technology could be superseded by solid state recording at some date in the future. Therefore the investment in CD type technology has to be written off before the time that any new technology means that the manufacturer will no longer support the old CD technology.

Developments in telecommunications may also have an impact in this area. For instance it would be possible to consider audio books stored on a central computer and transferred to the user's machine over the telephone line. If a book used 2 Gigabits, then it would take 20 minutes to transfer at 2 Mbits/sec (via copper wire connection) and 20 seconds at 155 Mbits/sec (via fibre optic connection). However it is now technically possible to transfer data at 2 Gigabits/sec on an optical fibre, which would reduce the time to 1 second. If this was ASCII text, then the whole Encylopaedia Brittanica could be transmitted in half a second.

Despite considerable effort devoted to the technological development of electronic mobility aids, their market penetration has been very low. In recent years, there has been more interest in orientation systems. Typically these involve infra-red transmitters which are modulated with a speech message. The blind user carries a small receiver which gives the speech message via a loudspeaker or an earpiece. The transmitters are typically mounted at street corners, on light-controlled pedestrian crossings (to give the status of the lights), and on buses (to give the destination of the bus). A different approach is to use tag technology as used in shop security systems. In this case, the tag indicates to a machine the presence of a blind person and the facilities they require; the tag may be pre-coded or controlled by the user.

There has been interest in utilising geographic information systems which are being developed for the sighted population. Many of these systems not only include geographic information but also information such as bus timetables. However there are many problems to be overcome before these systems are of practical use for a blind pedestrian; the main ones are loss of GPS signal close to buildings, and the high cost of creating and updating suitably detailed geographic information systems.

Self-service terminals are being used by the general public for an increasing range of applications. The increasingly sophisticated terminals offer the user a bewildering number of choices which can cause problems for users who are elderly or have a disability. To help these users it is possible to modify some terminal interfaces to meet individual needs (eg large characters on the screen of a cash dispenser or modify the frequency response of a public telephone).

With contactless card systems, a card is placed close to a read/write station (in any orientation). Having no card insertion would help people in wheelchairs who cannot reach the slot for the card reader, those with hand tremor or arthritis, and blind persons. Systems for interrogating cards at a distance of a few metres were developed for road charging, but this technology could have numerous benefits for blind and physically disabled persons (eg an audible signal for locating the appropriate terminal or trigger an audio message at the entrance to a bus giving the destination of the bus).

The interface requirements of the individual user could be stored on the smart card, as long as an international standard is agreed for the coding of this information. One possibility is to code details of the individual’s impairments; an alternative is to code the user’s preferred interface on the card. The coding of impairments does not provide precise details of the user’s requirements, and coding the preferred interface could give problems if the same card is used in a number of very different types of terminal. One possibility would be to code some combination of disabilities and user requirements.

In the longer term, technological developments in other fields could have benefit for those working with visually disabled persons. For instance, virtual reality technology could provide realistic simulations of visual defects including fields, acuity, colour discrimination and effects of illumination; in addition, multiple handicaps could be simulated. Such a system might be useful for evaluating proposed public buildings.

There is a danger of there being an increasing mismatch between research being done and the needs of the users. For instance, ten years ago the main users of synthetic speech devices were blind computer programmers as an aid to employment, but in the next few years older blind persons will need to use speech output devices to control domestic equipment such as microwave ovens. It is not obvious that those working on speech technology appreciate that 35% of the visually disabled population have a hearing deficit. Therefore there is an important role for user organisations to ensure that research workers are aware of the present and future unmet needs of visually disabled people.


Bruce, I., McKennell, A. & Walker, E. (1991) Blind and partially sighted adults in Britain: The RNIB survey. London: HMSO.


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