Biomedical Engineering Reference
In-Depth Information
10.5 Evaluation of Visual, Perceptive, and Motor Functions: Clinical Case 2
The patient can evaluate after having bandaged his RE to counterbalance diplopia and
without wearing the glasses prescribed for a slight myopia and astigmatism. There was a
vertical nystagmus movement more evident in the RE at the beginning of the evaluation
that successively also appeared in the LE. The patient could follow horizontal movements
only by completely moving his head, whereas he could more easily follow vertical move-
ments without needing to move his head too much. A least eye movement was observed
toward the nose direction. There was no great difference between the RE and LE. The
monocular sight evaluation was 1/10 for the RE and 3/10 for the LE both at a distance and
from a proximal point; however, we recommend using characters 5 mm or larger.
There was a slow convergence movement, and it was not possible to elicit efficient sac-
cadic movements, but, even in this case, the patient could compensate by using the move-
ment of his head. He could perform a correct scanning of stimuli adequately segregated in
a stimulus. The peripheral awareness of the stimuli was normal.
The global framework of the patient was quite complex. The brain damage caused a vari-
able-angle strabismus and a vertical nystagmus in both eyes, more evident in the RE. This
implies a diplopia, which during the evaluation was not compensated for by bandaging
of the nondominant eye. In cases such as this one, patients complain mainly about diplo-
pia, which is even more disturbing than possible blurred or unfocused images because of
ametropias. In this case it was not possible to use compensatory prismatic lenses because
of the variability of the deviation angle; therefore, the only possible solution was to ban-
dage the LE to enhance the remaining vision.
The patient used an ophthalmic correction for a slight myopia and astigmatism. During
the evaluation the usual glasses were taken off to favor focusing at a test distance of 50 cm.
It is useful to consider that in the range of age of the patient ( 37.6 years of age), it is pos-
sible to observe the first signs of presbyopia.
The patient was only able to perform horizontal pursuit movements with complete
involvement of his head. This shows a sufficient foveal functionality that stimulates motor
responses, first of all ocular and then also compensatory, such as the movement of the
head and the trunk, to keep the image inside of the macula region. However, in this partic-
ular case this causes the performance to slow down. The vertical pursuit was less difficult,
and the patient could perform it with a smaller movement of his head. The convergence
movements were possible, but slow. This led us to use a single working distance where we
placed all of the objects that the patient should see.
The evaluation of the visual acuity showed a marked reduction in the RE (1/10) and the
LE (3/10) from a long and a short distance. Regarding the RE, these results showed an
ability to recognize 3-mm letters at a 50-cm distance. This figure was obtained in the best
possible conditions with isolated stimuli and without any pressure. The suggestion was
therefore to use a character size of at least 5 mm to make the recognition easier even when
the fixation was not perfectly centered on the letter itself. At the same time, the letter was
not too big and the patient was not forced to shift his look when scanning.
It was impossible to elicit a saccadic movement oriented toward a definite stimulus
because the patient even in this case compensated with his head by turning toward the
significant element in his perceptual space. These movements obviously result slower
than a saccadic movement and they are not adequate to read fluently and with continuity.
Even the accuracy of the movements was very low, and it is extremely easy to point on
an unnecessary stimulus when the movements are very close to each other. To increase
