Strabismus - Fundamentals of Clinical Ophthalmology.pdf

STRABISMUS
In attempting to elevate the eyes, they may
roll up and out, simulating a V pattern of
movement. The parents of the child describe
one eye rolling up under the lid. This is the
result of Hering’s Law. If the eyes are straight in
primary gaze and on downgaze, treatment is not
advised. Spontaneous resolution has been
reported in some cases.
In children with marked head posture and
with the affected eye having up to 16 dioptres of
hypotropia, tenotomy of the superior oblique
tendon and sheath usually improves the vertical
deviation, although in some cases overaction of
the inferior oblique may occur and require
surgery.
The conjunctiva is incised 10 mm from the
limbus between medial rectus and superior
rectus and the muscle is isolated. Some advise
excision of the tendon, preserving the fascial
attachments, others advise a silicone expander.
Acquired Brown syndrome may be caused by a
nodule on the superior oblique tendon
preventing smooth passage through the trochlea.
The syndrome may also be due to collagen
disease, for example rheumatoid arthritis. Such
patients often notice a click 8 whilst conservative
management with anti-inflammatory agents,
including local injection of corticosteroid in the
trochlea, is reported to be useful.
Moebius syndrome
Moebius syndrome is diverse in the severity of
its presentation. It is thought to result from an
ischaemic insult in the first 5–6 weeks of
pregnancy. The paresis affects the sixth, seventh,
and often bulbar cranial nerves. Moebius
syndrome is of interest because it has aplasia of
the sixth nerve nucleus in common with Duane
syndrome and similarities are reported. The
clinical evidence of anomalous innervation of
lateral rectus is matched by the frequency of
gaze palsies apparent. Although an association is
reported, gaze palsies may be overlooked.
Surgery can be surprisingly successful. The
possibility of preservation of convergence and
substitution of convergent movement on lateral
gaze simulating sixth nerve palsy rather than
gaze palsy explains some presentations.
Congenital extraocular
muscle fibrosis syndrome
This autosomal dominant disorder is also
reported as being sporadic. The dominantly
inherited group reported by Gillies suggested
anomalies in the lateral ventricle. 9 More detailed
studies by MRI raise the possibility of a defect in
neuronal migration. The bilateral ptosis and
complete inability to elevate the eyes limits
options for surgery. Although the possibility
remains that part of the ptosis is pseudoptosis
due to inability to elevate the eyes we have not
had much improvement from recession of the
inferior recti. In addition to the studies
mentioned above, we have seen three sporadic
cases. All appear to have normal intelligence.
Surgery has not improved them cosmetically.
Strabismus fixus variants of muscle
fibrosis syndrome
This condition seen in childhood is
characterised by restriction of one or more
ocular muscles and may be uniocular. In our
experience, the child may fix with the eye with
the more restricted movement. This is important
to recognise. In one case, a 5-year-old child
referred to the university department had
marked abnormal head posture with face turn
to right, chin down, and marked limitation
of movements of the left eye. The eye with
restricted movement had not been recognised as
the fixing eye and the eye with full movement
had been patched, resulting in dense amblyopia.
At surgery, a forced duction test to the left eye
revealed inability to move the eye from an
adducted position and inability to elevate the left
eye. Surgery involved tenotomy of left medial
rectus, transposition of lateral halves of superior
and inferior rectus of the left eye and recession
of the medial half of left inferior rectus.
78