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Blind and Low Vision Users

Edward Hung (
Department of Computer Science
University of Maryland
College Park, MD 20742 USA
May 2001

Introduction Recommendations Guidelines Web sites Suggestions Resources


Numerous countries have passed legislation encouraging or even requiring accessibility in different settings, ranging from the general to the very specific. Different countries have different laws. One of the most critical laws is Section 508 of the Federal Rehabilitation Act in the United States, which specifies that starting from June 21, 2001, the U.S. government shall stop purchasing any information technology that is inaccessible to people with disabilities, nor will it make available for public use any information technology that is inaccessible (U.S. Federal Information Technology Accessibility ( Universal usability of web sites is a growing concern in the US  and worldwide.

By definition, accessibility is a category of usability: software that is not usable by a particular user is not accessible to that person. Just like other usability measures, it is necessary to define accessibility with respect to the user task requirements and needs. For example, graphical user interfaces are not very accessible to blind users, but relatively accessible to deaf users.

When we come to accessibility of web design, we will say that accessible web design is a sign of good web design. A lot of the information on the Web is not accessible to people with disabilities because of poor design. While many web site managers and developers accommodate various browser constraints, most of them do not realize that they are developing sites that people with disabilities have difficulty in navigating, or in many cases, cannot navigate at all (Microsoft Accessible Web design guidelines (

The purpose of this article is to provide recommendations, guidelines, examples and resources to web site developers on how to develop web sites accessible to users that are blind or have low vision.

People with visual disabilities are individuals who are blind, have low vision, or have color blindness. In this article, we will consider users with blindness and low vision.  For accessibility to color blind users and the user of color and color contrast, readers can refer to the related articles in Universal Usability Practice: Color vision confusion and Elderly. A blind person is one who cannot use a visual display at all. These are users who read Braille displays or listen to speech output (from a screen reader) to get information from their systems. Users with low vision have a wide variety of visual capabilities.  Estimates suggest that there are approximately 9-10 million people with low vision. A person with low vision can be considered to be someone who can only read print that is very large, magnified, or held very close. (Sun Microsystems' Accessibility Program ( From the statistics by American Foundation for the Blind, there are at least 1.5 million blind and visually impaired adults in the United States using computers. (American Foundation for the Blind (

The World Wide Web Consortium (W3C) ( gives the definitions of the following terms (the three pictures below are from NCSA Mosaic Access Page (

Screen reader

Braille display

Screen magnifier

Some organizations or companies also consider screen readers to include software that provides access to graphical user interfaces by providing navigation as well as a Braille display or speech synthesized reading of controls, text, and icons.

The rest of this article gives general recommendations for the goals of improved design in Section 2. Then Section 3 provides specific guidelines for web site developers to make their web sites accessible to blind and visually impaired users. Section 4 gives examples of good web sites with links and analysis. Future progress needed for practitioner and researchers is suggested in Section 5. Finally, resources including web links, organizations and papers are given for readers’ reference in Section 6.

General recommendations

This section states briefly the main goals of accessibility that a good web design should achieve.


Goals of accessible web design relative to blind users are:

Low Vision

Our goals of accessible web design relative to low vision users are:

Specific guidelines

This section provides the guidelines in details for designing accessible web sites. The guidelines are products by selecting and combining guidelines from the following: 





The guidelines for designing web sites accessible to blind users will be given first, followed by that for low vision users. The [Priority] number in the guidelines is from Web Content Accessibility Guidelines 1.0. Besides, a useful article “Usability Heuristics for Evaluating Web Structure and Content for People with Visual Disabilities” can be found in


1. Text equivalent

A good web site provides text-based means of conveying all essential information. It also provides essential information via text because text can readily be output to a speech synthesizer, other sound output device, or a Braille output device.

Blind users have screen reading software that can read the text contents of buttons, menus, and other control areas but screen readers cannot read the contents of an icon or image, they can only read the descriptive label or accessible name associated with them. Meaningful names should be provided for user interface objects in their code. Meaningful names can allow some screen reading software to provide useful information to users with visual impairments. Rather than naming an eraser graphic "widget5", for example, the code should call it "eraser" or some other descriptive name, that users will understand if spoken by a screen reader.

Without such descriptive information, blind or low vision users may find it difficult or impossible to interpret unlabeled, graphically labeled, or custom interface objects. Providing descriptive information may provide the only means for access in these cases. As an added selling point to developers, meaningful widget names make for code that is easier to document and debug.

Provide a text equivalent for every non-text element and embedded objects (e.g., via "alt", "longdesc", or in element content). This includes: images, graphical representations of text (including symbols), image map regions, animations (e.g., animated GIFs), applets and programmatic objects, ASCII art, frames, scripts, images used as list bullets, spacers, graphical buttons, sounds (played with or without user interaction), stand-alone audio files, audio tracks of video, and video. [Priority 1]

1.1  Good ALT text for all graphics.

1.2  Proper use of image maps

1.3  For any time-based multimedia presentation (e.g., a movie or animation), synchronize equivalent alternatives (e.g., captions or auditory descriptions of the visual track) with the presentation. [Priority 1] Readers can also refer to a related article in Universal Usability Practice: Textual equivalents for audio/video representations of content.

1.4 Alternatives to all controls and applets

Provide an alternate page that uses static text and graphics for displaying information, and standard links for input

Use explicit labeling of content and structural elements.

1.6 For using Internet Explorer 4

1.7 Finally, select all text and copy it to the clipboard, ensure it makes sense when pasted into a word processor.

2. Auditory description

3. Good Keyboard Navigation

Screen reader software provides access to graphical user interfaces by providing navigation as well as a Braille display or speech-synthesized reading of controls, text, and icons. A person who has a visual disability will not find the mouse useful because it requires hand and eye coordination. Instead, this person must navigate the Web page using only the keyboard. For example, the Tab key is used to move the focus to the item that needs to be selected. A screen reader then announces the item so the user knows where the focus is on the page.

The blind user typically uses tab and arrow controls to move through menus, buttons, icons, text areas, and other parts of the graphic interface. As the input focus moves, the screen reader provides Braille, speech, or non-speech audio feedback to indicate the user's position. For example, when focus moves to a button, the user might hear the words "button -- Search", or when focus moves to a text input region, the user might hear a typewriter sound. Some screen readers provide this kind of information only in audio form, while others provide a Braille display (a series of pins that raise and lower dynamically to form a row of Braille characters). Finally, the user can press a specified key (e.g. the Enter key) instead of "clicking" the mouse button.

For persons using screen reading software, they can "view" (hear) only one word at a time and must rely on their own memory to integrate portions of a document.

5. Use Bobby (, the analysis tool, to examine your pages.

6. Provide alternative access to critical information. Provide non-Web access (e.g., email, phone, fax) to critical information or graphics that cannot be easily described in text.

Low Vision

For designing accessible web sites to low vision users, the web site developers can also refer to the guidelines for blind users. Most of them can also be applied here.

1. Large font size

The common theme for low vision users is that it is challenging to read what is on the screen. Those who have low vision need the assistance of a hardware or software magnifier to enlarge the text beyond simple font enlargement. Although many users employ screen magnification hardware or software to enlarge their view, performance and image quality are improved if larger font sizes are available prior to magnification.

2. Configurable font size
All fonts, including those in text panes, menus, labels, and information messages, should be easily configurable by users. There is no way to anticipate how large is large enough. The larger fonts can be scaled, the more likely it is that users with low vision will be able to use software without additional magnification software or hardware.
3. Option of audio
A related problem for users with low vision is their limited field of view. Because they use large fonts or magnify the screen through hardware or software, a smaller amount of information is visible at one time. A limited field of view means that these users easily lose context. Events in an interface outside of their field of view may go unnoticed. These limitations in field of view imply that physical proximity of actions and consequences is especially important to users with low vision. In addition, providing redundant audio cues (or the option of audio) can notify users about new information or state changes.
4. Minimize the users' memory load.
For persons using screen magnification software, the effective size of the computer screen can be very small. Therefore, low vision users must rely on their own memory to integrate portions of a document. Please refer to the fourth guideline for blind users.
5. Use the High Contrast option in the Accessibility Options section of Control Panel, restart the browser, make sure the page is still readable.
6. Minimize Visual Strain

7. Enable the user to locate information quickly by providing efficient methods for search and navigation.

8. Resize the browser window larger and smaller to see whether there is any problem in the layout of the page because low vision users using magnification software may have a smaller effective size of the browser window.

14. Examples of Successful Web Sites

This section provides some good examples of web sites accessible to blind and low vision users.

4.1 American Foundation for the Blind (AFB)  (

4.2 Lighthouse International (

4.3 Adaptive Technology Computing Site (

4.4 (

4.5 ET Royal National Institute for the Blind (

4.6 National Federation for the Blind (

4.7 BCAB: British Computer Association of the Blind (

15. Future Progress Needed

Researchers should consider automatic analysis of web pages to check its accessibility to blind and low vision users. Bobby ( is a good example for web page analysis, but there is still room for improvement. Automatic correction will be a great help for web site developers. Another possibility is automatic translation of inaccessible web pages to accessible web pages. Moreover, researchers should work to improve software and hardware for blind users or low vision users so that it is easier for them to access web contents.

Practitioners should collect experience and develop better guidelines and set standards so that web site developers can achieve accessibility of their web sites more easily.

16. Resources

6.1 Legistration

6.2 Organization
6.3 Guidelines
6.4 Analysis tool
6.5 Products
6.6 Links
6.6 Newsgroups
6.7 Books
6.8 Papers

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