Design Considerations for Visual Output
When a web site, or the output from any type of computer software, is read by a person with a visual impairment, this person may be using one or more adaptive methods of decoding the information:
A. unmodified, reading by sitting up close to the screen, or by using a larger monitor;
B. enlarged with a handheld magnifier;
C. enlarged with software;
D. enlarged with an attached screen magnifier;
E. speech; or
F. refreshable braille.
Each of the above methods will have varying impact on the way the software is viewed. For example, types B and C, above, result in only part of the screen being visible at any one time, with manipulation required to get to other parts of the screen. Method D may cause less contrast on the screen, especially if room or window glare is reflecting off the screens. Ways E and F will give minimal information about pictures and graphics, if any.
Following are the main issues to keep in mind when designing a computer display which may be viewed by a person with a visual impairment. These comments are particularly addressed to those who design web pages for the internet, although all teachers and technology managers should keep them in mind.
To see samples of pages which progressively integrate these design features, click on this sentence.
(1) Size of letters, figures, and spaces
(a) larger items may be easier to see for people with reduced acuity.
(b) smaller items may better fit into the remaining visual areas of those who have a limited field.
(c) bolder print may be easier to see.
(d) larger spaces between letters and lines may help the reader to discriminate details.
(2) Contrast
Higher contrast will always be easier to see. Keep the backgrounds plain and the colors distinct. For some visual conditions, white letters on a black background may be best; light colors expand and that means letters appear thicker to them. For some specific conditions, yellow on blue is easier to see. Some people may prefer white on red, or any one of the myriad of possible combinations. When you don't know who the reader will be, go with the white on black.
(3) Simplicity
Simpler figures will be easier to decipher. For example, a detailed drawing of a tiger in the grass may be difficult to see; a simple line drawing of a tiger on a plain background wil be easier to see. Fonts which are italized, cursive, or all in capitals or which have serifs are generally harder to read.
(4) Linear design
Because people with visual impairments may have trouble scanning the screen, or may be accessing the information via speech, refreshable braille, or large print, avoid having information that is "all over the place", or that is enclosed in tables. Do not use frames, or have an alternate pathway without frames.
(5) Graphics
Keep graphics to a minimum. For those that are necessary, include an alternative description ("alt text") that describes them. Have an alternate pathway with screens that have no graphics.
To see samples of pages which progressively integrate these design features, click on this sentence.