Assistive Technology Applications For People With Visual Impairments

Visual impairments are anatomic or functional disturbances in one's affecting central visual acuity, field of vision, color perception, or binocular visual function (Andrew, 2004). A person with a visual impairment typically has a visual acuity ranging from 20/70 to 20/200. Many eye conditions are degenerative in nature and can eventually lead to partial or even total blindness. Blindness is legally defined as a central visual acuity not exceeding 20/200 in at least one eye with best correction or a limit in the field of vision to such a degree that its widest diameter subtends an angle of no greater than 20 degrees (Andrew, 2004). This definition of legal blindness was established by the American Medical Association in 1934 and is recognized as law in most states. Legal blindness in children is usually caused by tumors, infections, injuries, or retrolental fibroplasia (typically found in babies who have had oxygen therapy based on premature birth). Diabetic retinopathy, cataracts, glaucoma, macular degeneration, infections, injuries, and genetic conditions are the most common causes of legal blindness to adults.

Some of the earliest AT was created for people with visual impairments. Braille, a system of reading and writing by touch, was invented in 1834 and is still used as a means to access written material. It is also believed that eyeglasses have been used to correct people's vision since the 13th century. Other AT devices and strategies are used to help people with visual impairments access computers and printed materials, navigate through different environments, and operate in school, work, and home environments.

Low Tech/No Tech Assistive Technology

Low tech devices and strategies can be used to assist people with visual impairments in many aspects of everyday life. The most common low tech AT device for people with various levels of visual impairments are eyeglasses, which are used to correct one's vision. Magnifying glasses have similar components to eyeglasses and are used to increase the size of text, images, or objects for people with visual impairments. Other low tech devices and strategies used by people with visual impairments to access printed materials include Braille, large print materials, and audio versions of materials such as books on tape. To help people with visual impairments succeed in school or work environments, some very simple low tech strategies can be implemented such as color coding materials with different colored paper and highlighters for various subjects, providing people with large print materials, and providing a scribe to help write dictated text. Navigating environments can be difficult for people with visual impairments, but there are low tech devices that can aid in this. These include the Hoover Cane, the white cane used in navigating environments to feel upcoming obstacles in order to avoid them, and seeing eye dogs which are used in a similar manner.

Mid Tech Assistive Technology

Mid tech devices used by people with visual impairments are typically household devices equipped with an audio output. Examples of devices in this category include talking calculators, talking watches, talking clocks, and talking thermometers that announce times or numbers. Most other vision-related mid tech AT devices are portable electronic devices used to help people with visual impairments complete everyday tasks. The best example of this type of device is an electronic bill reader, a device that reads and indicates the value of a monetary bill, providing independence in activities involving money exchange. Finally, universal design options included on many commonly used items, such as the speed dial or voice dial options on telephones are considered mid tech AT options that benefit people with visual impairments by minimizing the opportunity for a mistake in entering a phone number.

High Tech Assistive Technology

High tech vision-related AT devices primarily consist of computer or printed material access options. Computer access options include Braille keyboards, screen magnification software, screen readers, and text-to-audio programs. These devices provide people with visual impairments access to a computer by reading the contents of a computer screen to aid in navigation, magnifying the size of objects on the screen to an optimal viewing size, or reading letters that are typed to ensure accuracy. Another high tech computer access device is the Power Brailler, a device that connects to a keyboard and prints what is being typed both on the computer and a refreshable Braille display.

High tech devices are also available to help people with visual impairments access printed material. A direct access example is the Closed Circuit Television (CCTV), which projects a magnified image of desired printed material on a "television" screen. This type of devices consists of a camera focused on a tray where the printed material is placed. This camera captures an image of the printed material which is then displayed on a television screen. This material can be magnified, the contrast changed, and/or lines or words isolated for an individual with a visual impairment to see the printed material. The other high tech AT options are scan and read programs. These utilize a scanner and a computer to transform printed material into a form that can be read to the user by the computer. This is more likely to be used by a person with a more severe visual impairment and entails an added step of scanning the document before it can be accessed.

Finally, there are high tech devices that can be used for navigation purposes. These devices are GPS systems worn by the user that indicate where the user is located, what streets and land marks the user is approaching, and where the user needs to turn to get to the desired location. These directions are indicated to the user through an audio output via a speaker or earphone. 

Back - Next