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Children with physical disabilities are usually limited in their range of movement for their hands and arms. They may also have uncoordinated movements which can be controlled, to some extent, by gripping onto something, such as the corner of the device.
It is very important that when using direct access, or any of the other access methods, that the device is positioned in such as way that it is easy, comfortable and not tiring, for them to access for extended periods of time. If the communication aid
requires too much effort or causes discomfort or pain then the child is unlikely to use it.
Thinking about the questions that need to be asked
The positioning of a switch as an input device, so that the user does not find it awkward or tiring, is a very important part of the AAC assessment.
Understand the User
How will the switch be controlled? Head, mouth, hand, knees or foot? What pattern of movement is possible and how consistent? Fine motor pattern or gross - more random? How much pressure or force is possible (as this determine the required
stability of the switch in a clamp or on a mat)?
Each switch may require a specific connection, each type of mount may require a specific clamp, fixing or nonslip mat. Not all switches and mounts are compatible and most switches can have several options in terms of positioning depending
on the user and the setting.
This will depend as much on the way the user activates the switch as it does not the setting. Will the switch be activated when the user is in a wheelchair, bed, at a desk or on the floor? Does the switch need to have additonal clamps around the wheelchair tubing, perhaps when using foot or knee access or a head fixing. If the switch is on a desk does it need velcro or a sticky mat or wedge to stop it slipping or provide the right angle?
Review and review again
Evaluating the success of any positioning is ongoing. Repetitive strain injuries can occur, just as they can when we sit at the computer and use a mouse incorrectly for any length of time. Abandonment of the AAC device may not be because communication is difficult, but because the assistive technology is uncomfortable to use. Keep checking and updating!
Any type of switch is dependent on the child’s reliable movements. It follows that positioning the switch accurately will be very important in order to use these movements.
Take for example a Microlight switch which is very good at activating anything electronic, using very small movements with very little force. The switch requires just 0.7mm of movement in order to cause something to happen and is often used with
very small finger or hand movements. In order to be reliable the switch would typically be placed very close to the area of the body part used to activate the switch.
Often the easiest way to position switches is to use Velcro boards such as the Maxess trays or by fixing Velcro directly to the wheelchair trays.
Getting head switches into the right position is also very important. It’s essential
that the switch can be easily activated through a purposeful head movement, such as a tip to the left or right, but that the switch does not get activated during typical head movements, such as turning to see someone.
There are a number of specialist mounts and poles such as those designed by Daessy that can be used to get switches in the right location, usually attached to the child’s wheelchair.
Eye Gaze Video - Reviewing use
Watch the video and think about all of the issues that had to be considered in setting up this system for her use
Even eyegaze requires careful positioning. It must be mounted using a floor mount, desk mount, or attached to the wheelchair, so that the device is held around 60cm away from the child’s face. If it is not in the best position then accuracy will be poor
and the child will give up quickly!
Each eyegaze system has a Track Box size rating. This indicates
the amount of movement that a child can make and still have accurate eyegaze. It also indicates the amount of tolerance for the positioning. As an example, the Tobii Dynavox IS4 camera found in the EyeMobilePlus and i-Series devices has a track box
of 35cm by 30cm. This represents an invisible box around 60cm directly in front of the camera. The eyegaze will work as long as the child’s eyes are within the box. The LC Edge camera, by comparison, has a tracking box that measures 7.6 x 6.4cm
so requires the user to keep their head still.