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Nystagmus
Description
Nystagmus is the involuntary, rhythmical, oscillations of
one or both eyes, in any or all fields of gaze.
Pendular: undulating movements of equal speed, amplitude,
and duration, in each direction or
Jerky: with slower movements in one direction, followed
by a faster return to the original position.
Horizontal:from ulternating between, left and right
Vertical: ulternating between up and down
Oblique: moving in a diagonal plain
Rotary\circular: In a circle.
or any combination of these:
Generally, the faster the rate, the smaller the amplitude
(and vice versa). The defect is classified according to
the position of the eyes when it occurs.
Grade I occurs only when the eyes are directed toward the
fast component;
Grade II occurs when the eyes are also in their primary
position;
Grade III occurs even when the eyes are directed toward
the slow component.
The cause of nystagmus is unknown. Reduced acuity is
caused by the inability to maintain steady fixation.
Head-tilting may decrease the nystagmus and is usually
involuntary (toward the fast component in jerky
nystagmus, or in such a position to minimize pendular
nystagmus). Head nodding often accompanies congenital
nystagmus.
Congenital nystagmus of the pendular type usually
accompanies congenital visual impairment (e.g., corneal
opacity, cataract, albinism, aniridia, optic atrophy,
chorioretinitis).
There is no known treatment, however, certain types of
jerky nystagmus (commonly Grade I types) show spontaneous
improvement in childhood (up to age 10). This type may
also be amenable to muscle surgery (essentially, a
repositioning of muscles to take advantage of the point
of least nystagmus, or position of relative rest).
With the exception of brief experiences of oscillopsia,
most individuals with nystagmus perceive objects as being
stationary. It is believed that the brain is responsible
for the perceptual adjustment.
Educationally, children with nystagmus (who may tend to
lose their place in beginning reading instruction) may be
helped through the use of a typoscope (card with a
rectangular hole, to view one word or line at a time) or
an underliner (card or strip of paper to "underline"
the line being read). As children with nystagmus mature,
they seem to need these support devices less often.
Beth's Nystagmus: a personal account of aniridia and
nystagmus
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