Strabismus - Fundamentals of Clinical Ophthalmology.pdf

STRABISMUS
of the eye with good vision will allow the
amblyopic eye to recover vision. Indeed, if
occlusion is prolonged the occluded eye
becomes amblyopic. This reversal of amblyopia
is referred to as occlusion amblyopia. It is
important also to recognise and treat the other
forms of amblyopia, namely pattern and
anisometropic, which may also contribute to the
poor vision.
Arising from the above are the three
principles of management that should be
followed before surgery is considered:
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confirming that the amblyopia is strabismic in
type
ensuring an accurate refraction for each eye,
and
ensuring occlusion therapy with a regime
appropriate to each individual case.
These three principles and the exclusion of
central nervous system or ocular pathology are
essential to observe before any consideration is
given to strabismus surgery.
Principles and strategies for
non-surgical therapy of strabismus
and amblyopia
Confirming strabismic amblyopia
Careful examination and refraction will
usually allow confirmation of the nature of the
amblyopia. However, unilateral optic nerve
hypoplasia is a pathological lesion sometimes
missed, the halo around the small disc being
mistaken for the neural rim. Posterior lenticonus
may be missed early and as it is frequently
followed by the development of progressive
cataract in infancy, it may contribute to a pattern
deprivation amblyopia. If there is doubt the
matter is usually readily resolved with the
additional information from examination under
anaesthetic, including biomicroscopy and
confirming refraction.
Confirming refraction
As pointed out in the text referring to
assessment (see Chapter 6), it is essential to gain
the trust of the child and the parent. Staff should
not be in white coats. Eye drops may be a
frightening experience for the child. With a
particularly anxious and frightened child, there
may be wisdom in writing a prescription for
atropine 0·5% or 1% eye drops depending on
the age of the child and instructing the parents
how to instil the drops morning and night two
days before the visit and on the morning of the
visit. However, parents should be warned that
reactions may occur in the form of irritability,
flushing and raised temperature, particularly
in the very young and more often in children
with cerebral palsy or impaired temperature
control.
Prescription of glasses
No child or infant is too young to wear
glasses. The decision to order glasses is
frequently sufficient for some parents to seek a
second opinion, so it is important to spend time
speaking to the parents so that they understand
the underlying reasons. In the premature infant
glasses are usually deferred at least until
corrected age is about term. Our experience is
that in the early period of life, particularly in
infants born prematurely, there are changes
toward emmetropisation that justify watching
carefully to see if refraction is stabilising before
ordering glasses. Prescription of glasses to
correct hypermetropia in an accommodative
strabismus is usually in the second or third year
of life. Less commonly, hypermetropia may be
among the spectrum of presentations of
congenital esotropia.
Clinical tips
It is important to remember that smaller
degrees of hypermetropia prescribed after
surgery for congenital esotropia may be effective
in correction of residual deviations.
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