Biomedical Engineering Reference
In-Depth Information
the accuracy of the gaze, the stimuli should therefore be less frequent by increasing the
distance between each other. This suggestion is in contrast with the previous one, relating
to the difficulty to perform horizontal movements; therefore, in this case the best combina-
tion of separation and collocation must be assessed empirically.
10.6 Visual Training
These short notes illustrate one of the possible alternative solutions offered by optometry.
In many patients the limited visual skills may be improved through special techniques that
stimulate the vision and are reunited under the denomination of visual training (Adler 2002;
Gallaway 2002; Shainberg 2010). Visual training is not only a specific training for the eyes, it
is also an integrated sequence of procedures that increase the efficiency of vision, especially
through multichannel stimulation protocols (sight, hearing, touch, proprioception, balance,
etc.) and through the integration of cognitive aspects (Martinoli and Delpino 2009).
The reason to mention this opportunity is that many patients have been observed who
show such a low visual ability that the range of alternative choices in the assistive technolo-
gies is very limited but also show a relevant potential. To obtain even the slightest improve-
ment can allow for the use of more efficient instruments with a positive feedback in addition
to the improved vision, so that a positive cycle is triggered. This can be true in cases in which
marked difficulties in slow pursuit while sitting can be reduced in a supine position.
Evidently the interferences induced by the need for postural control eliminate every
possibility of working efficiently when sitting. For these children the use of a computer
provided with a cursor would not be possible because they would not be able to follow
the trajectory and would be forced to search for the cursor every time they lost fixation.
Alternatively, a large cursor, so that it could be easily recuperated, or an excessively slow
cursor should be used, but a great part of the interactive functions would be lost. These chil-
dren should be asked to follow some visual training programs that are aimed at enhancing
their pursuit function in different postures. The description of the techniques used is not
related to the aim of this topic, but in short we can state that we act starting from the situa-
tions at a minimum visual and postural load and then we gradually increase the interfering
elements in the most ecologic perspective (Padula 1996, Sabel and Kasten 2000).
The use of instruments that cause unnatural alterations, as well as the use of stereoscopic
and polarizing systems is limited, except for the twin prisms. This kind of lens produces
a distortion in the perceived environment that induces a reflex of posture adjustment. As
long as the child develops even a minimal pursuit skill, his/her ability to use more effi-
cient assistive technologies can be verified.
10.7 Conclusions
This chapter aimed at showing the role of the visual process, conceived as a complex skill
involving both peripheral and central aspects, when choosing the appropriate assistive tech-
nology. Some procedural and technical aspects have been purposefully omitted because
they are too complex to be integrated in this project. We tried anyway to provide some
simple operative advice to the optometrists who are approaching the world of the ATA.
