For some people with visual impairments the standard size of letters on the screen or printed in documents are too small for them to read. Some people cannot distinguish one color from another. Fortunately, specialized hardware and software can make computer systems usable by individuals with visual impairments.
Most individuals who have visual impairments can use standard keyboards, but large-print keytop labels are sometimes useful, particularly when they are learning to type.
Special equipment for individuals who are visually impaired can modify displays or printer output. Computer-generated symbols, both text and graphics, can be enlarged on the monitor or printer, thereby allowing individuals with low vision to use standard word processing, spreadsheet, electronic mail, and other software applications. For individuals with some visual impairments, the ability to adjust the color of the monitor or change the foreground and background colors is also of value. For example, special software can reverse the screen from black on white to white on black for people who are light sensitive. Antiglare screens can be easier to read. Speech output systems are also used by people with low vision.
Scanners with optical character recognition can read printed material and store it electronically on computers, where it can be read using speech synthesis or printed in large print. Some hardware and software vendors also provide large-print or American Standard Code for Information Interchange (ASCII) versions of their documentation.