Web Access for the Blind
In order for a website to be viewed by visually impaired or blind visitors, website development must be designed with accessibility. Blind computer users use common browsers such as Internet Explorer or Mozilla Firefox and usually use screen readers that read the screen and send the information to a speech synthesizer or Braille display. Screen readers can provide output but to Synthetic Speech Systems.
A synthetic speech system is based on two operations; the synthesizer for sound (speaking,) and the screen reader that instructs the synthesizer. These are also called text to speech systems and abide by phonemes and grammatical rules of a language for accurate pronunciation. They are not perfect. Certain words and spelling variations can be mispronounced. Working in conjunction with a PC soundcard, the synthesizer software produces speech. Synthesizers and screen readers come as a unit when purchased.
Screen readers send commands to synthesizers from the keyboard and computer screen.
The synthesizer can be instructed to read a single word, line, or full screen of text. They can also be commanded to find text, spell words, focus on a specific picture and track the mouse pointer. Many have advanced functions such as reading highlighted text, menus, or locating certain colors and even locate information on spreadsheets.
When a screen reader reads a web page some can read the page intelligently and provide structural information. Other users might not be using a screen reader at all to access your web page and instead use a browser designed for blind users. These browsers can usually interpret page structure. These special browsers are often behind in technology development of the more popular browsers and might be less secure and unable to display some flash animations.
Evaluating Screen Readers
Questions to ask before purchasing screen readers:
What operating system will be used? What version? Microsoft Active Accessibility (MSAA) is a set of programming language enhancements and standards for programmers.
Are there required computer configurations (color schemes, common video cards, etc.)?
Does the screen reader include a synthesizer? Are other synthesizers supported?
Is there an accessible manual and tutorial in screen reader or other format?
Are there applications or programs that will not work with the screen reader?
How much of the speech is automatic as the user is performing standard Windows functions? Is this adjustable? Can voice speed be changed?
Introduction to the Screen Reader Video
Free Screen Readers
Mobile Screen Reader
Screen Magnification and Other Techniques
Some users with visual impairments access websites with screen magnification or use the browser and computer settings to adapt the screen to their needs. Web page design including colors and layout can help or hinder them.
Screen magnification makes text and graphics larger but allows only a portion of the page to be viewed on the screen so the user must continuously move around to see everything. Captions, graphic references, links, and their relationships are sometimes incoherent to these users.
The Visually Impaired Web User's Technology
Designing Accessible Web Pages
For making web site accessible, the most valuable resource available is the web site of the Web Access Initiative (WAI), part of the World Wide Web Consortium. There are guidelines for designing web pages. Most web pages have not been designed for optimum use for visually impaired visitors. Guidelines can be found at:
Web Content Accessibility Guidelines 1.0
Viewable with any browser: An accessible design guide.
The Trace Research & Development Center of the College of Engineering, University of Wisconsin-Madison. Trace has been a pioneer in the field of technology and disability since 1971.
Evaluating websites for accessibility.
HTML (Hypertext Markup Language) has the "alt" tag that can be used in every image to provide a brief description of the image. If the image is a link, the alt tag where the link goes. The addition of an alt tag for an image takes seconds to add and most web design software makes it easy to add tags.
Website Accessibility Design Checklist:
Website Accessibility Design Help
Simulate color blind visions and correct images for color blind viewers.
A web accessibility initiative from Utah State University
How Windows-Based Screen Readers Work.
The functions of screen readers are classified in five categories.
- Identifying and Reading Text and Graphics
When a screen displays text and graphics Windows temporarily stores the data in pixel format that that the screen reader cannot interpret. Windows-based screen readers intercept the data and store it in off-screen model (OSM). The screen reader then reads from the OSM.
- Identifying and Announcing the Function of Window Elements
Windows preserves the type of elements and most screen readers can reclaim this information. When there is an action required by the user to continue with a task the screen reader identifies the item and reports the appropriate course of action.
- Identifying Graphics
Icons, pictures, and graphics are reported in meaningful terms.
- Serving as a Cursor
To position the mouse cursor on a particular point on the screen, screen readers incorporate features which move the mouse pointer in straight rows and columns or by meaningful units such as words or characters, find specific text and position place the mouse cursor correctly. Keystrokes can simulate clicking.
- Providing the Information
Screen readers need to provide information as needed. Synthetic speech programs that focus on essential information rather than reading an entire screen in sequence are most effective.
Introduction to the Screen Reader video that explains how screen readers help people who are blind navigate and interact with the web.
Free screen readers.
Thunder is a free screen reader for people with little or no sight. Compatible with Windows 7, Vista or XP and available in 8 languages.
Optimizing web pages for hand held viewing.
Text to Speech (TTS):
How to configure and use Text-to-Speech in Windows XP and in Windows Vista
Acapela text to speech