Strabismus - Fundamentals of Clinical Ophthalmology.pdf

4 Childhood onset of strabismus
Childhood strabismus is distinguished by the risk
of amblyopia. The strabismus may be considered
in the context of a number of syndromes; those
that are predominantly horizontal (concomitant)
and without marked movement deficits and
those that are incomitant with more exaggerated
movement deficits. Both concomitant and
incomitant strabismus may be associated with
vertical muscle imbalance at presentation.
Concomitant horizontal deviations may develop
vertical deviations later with characteristic
alphabet patterns and need to be followed
carefully in order to obtain optimal outcomes.
These are most commonly seen in congenital
(infantile) esotropia and for completeness’ sake
will be discussed with this entity.
Amblyopia
Recognition and treatment of amblyopia is a
fundamental component of management of
strabismus. Principles of management are
essentially directed at early detection and
treatment to produce equal vision, only then
followed by strabismus surgery aimed at ocular
alignment. Assessment and management of
amblyopia are further discussed in Chapters 6
and 7. The basic science which underpins
clinical manifestations of amblyopia is discussed
in Chapter 1. Various forms of amblyopia may
be present in strabismus cases; for example,
there may be a combination of strabismic and
pattern deprivation amblyopia due to a unilateral
cataract or refractive cause.
Types of amblyopia
Strabismic amblyopia
Strabismic amblyopia is unilateral. It occurs less
frequently in untreated congenital infantile
esotropias (20%) compared with acquired infantile
esotropias (100%). 1 Intermittent exotropias, on
the other hand, usually do not produce strabismic
amblyopia, as there is fusion at near fixation.
Refractive amblyopia
Refractive amblyopia caused by uncorrected
ametropia may be unilateral or bilateral and
may involve a meridional component from
astigmatism. Anisometropic amblyopia may
occur if the refractive error is unilateral and may
be associated with strabismus in approximately
30% of cases. Aniseikonia from correction of a
large difference in refractive error appears to be
tolerated better in children than adults, and
should not be used as an excuse not to offer
glasses and occlusion. 2
Pattern deprivation amblyopia
The absence of patterned visual stimulation
of the fovea during the first few months of life is
particularly devastating. It is important to
recognise that amblyopia may occur as a result of a
media opacity such as congenital cataract, corneal
scar, retinoblastoma or vitreous haemorrhage.
Pattern deprivation amblyopia may be unilateral
or bilateral and may be associated with strabismus
if unilateral.
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