Types of Motor Disabilities
The key principle of web accessibility for users with motor disabilities is:
- Operable: because not everyone can use a mouse, click on small links, or operate dynamic elements effectively
Spinal cord injury
Spinal cord injuries can result in a state of paralysis of the limbs. Paralysis of the legs is called paraplegia. Paralysis of the legs and arms is called quadriplegia. Before we get into the details of how spinal cord injuries affect web access, let's go over some of the statistics:
- The average age at injury is 31.7 years.
- Males account for about 75% of those with spinal cord injuries.
- The leading causes of spinal cord injury are as follows:
- motor vehicle accidents: 44%
- acts of violence: 24%
- falls: 22%
- sports: 8%
- other: 2%
Individuals with paraplegia generally have no difficulty accessing the Internet. Individuals with quadriplegia, however, may have significant difficulties, depending on the type and severity of the injury. Some individuals with quadriplegia have some use of their hands, but not enough to, say, manipulate a mouse or type on a keyboard. Despite these limitations, individuals with quadriplegia are able to make use of assistive technologies that allow them to access the functionality of their computers.
Gordon Richins, Consumer Liaison at the Center for Persons with Disabilities at Utah State University, who has quadriplegia, shares his perspective on web accessibility.
Loss or damage of limb(s)
Someone who has lost one hand will still be able to use the Internet without too much difficulty. One-handed keyboards are available, which can completely compensate for the lack of the other hand, at least as far as computer access is concerned. However, someone who has lost both limbs may need to make use of other technologies, such as the ones used by individuals with quadriplegia (head wands, mouth sticks, voice recognition software, etc.).
Diseases and Congenital Conditions
Cerebral palsy is an injury to the brain (which is why the term "cerebral" is used), resulting in decreased muscle control (palsy). The condition usually occurs during fetal development, but can also occur at or shortly after birth. Common characteristics of cerebral palsy include muscle tightness or spasm, involuntary movement, and impaired speech. Severe cases can lead to paralysis.
Many people with cerebral palsy are able to use computers, but usually have a difficult time using a mouse. Their arm movements are often too jerky and unpredictable to use a mouse effectively. They can usually use a keyboard, or an adaptive keyboard, though more slowly than individuals without cerebral palsy. Oftentimes they will use keyboards with raised areas in between the keys, to allow them to place their hand on the raised area, then press their fingers down onto the key that they wish to type. Regular keyboards can be adapted to this same purpose by the use of keyboard overlays. This reduces the likelihood of errors while typing.
Muscular dystrophy (MD) is a genetic disorder in which the genes for muscle proteins are damaged. It is characterized by the progressive degeneration of the muscles. Muscular dystrophy can affect people at any age, but is most common in children. Individuals with mild MD can live a normal life span, while individuals with more serious cases can die in their teens or early 20s. The assistive technologies used by individuals with MD depend on the severity of the condition, but generally include the same technologies already mentioned (head wands, mouth sticks, adaptive keyboard, voice recognition software, etc.).
In individuals with multiple sclerosis (MS), the myelin (a layer of fatty tissue which surrounds nerve fibers) erodes, rendering the nerve fibers incapable of sending signals from the central nervous system to the muscles of the body. The milder cases of MS can result in one or more of the following symptoms: tremors, weakness, numbness, unstable walking, spasticity, slurred speech, muscle stiffness, or impaired memory. Severe cases can result in partial or complete paralysis. Not all individuals with MS experience all of the symptoms and, interestingly, the same individual may experience different sets of symptoms at different times. The types of technologies used are the same as for other motor disabilities.
Spina bifida is a congenital condition in which the spine fails to close properly during the first month of pregnancy. This causes the membrane around the spinal column to protrude through the back, resulting in a visible bulge, or sac on the back of the individual. In the more serious cases, the spinal column itself protrudes through this opening. Individuals born with spina bifida will likely experience motor difficulties, and possibly paralysis. In some cases, fluid can accumulate in the brain, which may also cause damage to the brain. Some individuals experience learning and language difficulties as a result.
Amyotrophic lateral sclerosis (Lou Gehrig's Disease)
Sometimes called Lou Gehrig's disease, Amyotrophic lateral sclerosis (ALS) is a degenerative disease that prevents neurons from sending impulses to the muscles. The muscles weaken over time, and the condition may eventually affect the muscles required for breathing, resulting in death. Symptoms include slowness in either movement or speech. The vast majority of cases of ALS are of unknown causes. About 5-10% of cases are genetically-linked. (See http://www.neurologychannel.com/als/ for more information.)
Arthritis occurs most often in the elderly, but can occur in younger individuals as well. Many people with arthritis are able to use a keyboard and mouse, but they do not always have the fine motor control sufficient to click accurately on small links, for example. More often than not, people with arthritis do not use assistive technologies at all, but some with more advanced arthritis may use a trackball mouse, voice recognition software, or foot pedals. Joint pain can cause fatigue, and limit the amount of time that the person is willing to spend on a computer maneuvering a mouse and typing on a keyboard.
Parkinson's disease (PD) is a disorder of the central nervous system that causes uncontrollable tremors and/or rigidity in the muscles. Individuals with advanced cases of Parkinson's Disease may not be able to use a mouse at all, and some are unable to use a keyboard. Sometimes the voice is affected as well, so that voice recognition software is not an option, though most people with PD have voices that are easily understood. Parkinson's Disease is most likely to occur later in life, but can affect younger individuals as well.
Like Parkinson's Disease, Essential tremor (ET) is a nerve disorder that can result in uncontrollable tremors. Essential tremor most frequently affects the upper body, such as the hands, arms, head, and larynx (which makes the voice more difficult to understand).
|Users may not be able to use the mouse.||Make sure that all functions are available from the keyboard (try tabbing from link to link).|
|Users may not be able to control the mouse or the keyboard well.||Make sure that your pages are error-tolerant (e.g. ask "are you sure you want to delete this file?"), do not create small links or moving links.|
|Users may be using voice-activated software.||Voice-activated software can replicate mouse movement, but not as efficiently as it can replicate keyboard functionality, so make sure that all functions are available from the keyboard.|
|Users may become fatigued when using "puff-and-sip" or similar adaptive technologies.||Provide a method for skipping over long lists of links or other lengthy content.|