Strabismus - Fundamentals of Clinical Ophthalmology.pdf

STRABISMUS
Figure 4.24 Left convergent strabismus in a child
with oculomotor apraxia, noted to have head
thrusting movements at 6 months (MRI shown in
Fig 4.25)
(a)
gliomas had nystagmus. 28 Sensory causes are
more commonly static but the diagnosis can
depend on the recognition of subtle signs. A
good rule is to assume the cause is sensory until
proved otherwise.
Sensory causes difficult to diagnose include
macular coloboma, toxoplasmosis and many
conditions that have an hereditary basis. Foveal
hypoplasia may be associated with albinism
or with complete aniridia. Oculocutaneous
albinism is usually obvious and is recessive in its
inheritance. Ocular albinism, less obvious
clinically, is usually X-linked, although 10% are
recessive. 29 Iris transillumination should be
looked for, and also in the mother. Other
conditions include Leber retinal dystrophy,
often suspected on its other association with
high hypermetropia. This condition also requires
genetic counselling as do congenital night
blindness and rod partial monochromatism.
Motor nystagmus is most often associated
with a null point for the nystagmus and
abnormal head posture. This may be in any
particular direction of gaze for the particular
case, usually in a conjugate field of gaze. By
contrast, in cases of Ciancia syndrome the null
point in each eye will be in a position of
convergence.
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(b)
(c)
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Figure 4.25 MRI scan of child with oculomotor
apraxia showing hypoplasia of the cerebellar vermis
(arrow) (a) and enlarged cisterna magna (asterisk)
(b, c)