Strabismus - Fundamentals of Clinical Ophthalmology.pdf

THERAPY OF STRABISMUS
Figure 7.3 Accommodative strabismus with
convergence excess. Executive bifocal glasses may
assist control. Note the junction of the bifocals
horizontally “splits” the pupil
● As a “rule of thumb”, astigmatism,
particularly if more than 2 D, is significant
enough to be amblyogenic and, if unilateral,
could be an asymmetrising factor in the
development of strabismus.
●
●
Children who are sufficiently myopic to justify
ordering glasses may reveal accommodative
strabismus with convergence excess when
wearing glasses, and may require surgery to
control the deviation.
Children with accommodative strabismus with
convergence excess may be helped to control
the strabismus by wearing executive bifocals. It
is important that the ophthalmologist checks
the glasses and ensures that the horizontal
junction between reading segment and the
distance lenses splits the pupil (Figure 7.3).
The reason for this is that as soon as the child
lowers the eyes to view a near object, the need
to accommodate is obviated.
● Anisometropic amblyopia has a more
prolonged critical period than pattern
deprivation and strabismic amblyopia, and
prognosis for improvement of vision can be
good even if treatment started after the age of
7 years.
Occlusion
Constant occlusion of the dominant eye is
still the most effective method of treating an
amblyopic eye. With a history that dates back to
the 18th century, it continues to be the preferred
method. Recent results of penalisation confirm
this. Understanding the sensitivity of the
developing infant’s visual system (see Chapter 2)
demands that occlusion in infancy be closely
monitored. Monitoring of eyes that have been
amblyopic or are at risk of amblyopia should
continue at least until the child’s visual system
has matured (usually at age 9–10 years). The
earlier the amblyopia is detected and the
younger the child or infant, the shorter must be
the occlusion.
Types of occlusion Full-time occlusion is
most easily implemented in the preverbal and
preschool child. However, after the age of
4–5 years and particularly at school, children’s
peer groups tease and indeed the poorer vision
in the amblyopic eye may make for learning
problems. Although not as effective, part-time
occlusion is well worth implementing in cases
where constant occlusion is not tolerated or
maintenance occlusion is required. As previously
mentioned, in our experience in university
clinics, children of school age are most often
only submitted to occlusion out of school hours
doing homework, or in the younger child given
play tasks demanding attention to near detail.
We have found even a half to one hour effective
in maintaining vision and even improving vision
that had been poor because of refusal to
cooperate in full-time occlusion.
Sometimes, with treatment of amblyopia, the
patient has refused to wear glasses. In those
cases with high refractive error or astigmatism,
the use of atropine in each eye once or twice a
week has been useful in the encouragement of
wearing glasses. Traditional occlusion and
partial occlusion of a lens to obstruct vision in a
particular direction of gaze, for example by
translucent paper, may have advantages over
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