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Intermittent exotropia is a common form of
strabismus , Patients with this
type of strabismus demonstrate
a duality of behavior in that they seem to be
completely normal during orthotropic intervals and
totally ‘turned out during periods of manifest exotropia.
Intermittent exotropia has been
classically divided into four categories :
I. Basic type
: The exodeviation
is the same at distance and at near.
II. Divergence excess type
:The
distance exodeviation is greater than the near.
III.
Convergence insufficiency type :The near
deviation is greater than the far .
IV. Simulated divergence excess type :The
patient presents initially with a larger
deviation at distance,
if
the patient has one eye patched for 15
to 30 minutes, then , take off the patch , If the
near deviation remains smaller, the patient
has true divergence excess. If the near deviation
equals the distance deviation, the patient
has simulated divergence excess exotropia .
Surgery
which is described for treatment of Divergence
Excess Intermittent XT must be planned for the
far deviation without regard for the near
deviation. Correction of the distance deviation
has no adverse effect on the near deviation.
Intermittent XT is
best treated with bilateral lateral rectus
recession. A table for surgery plan I usually follow:
5.0 mm OU/20-25 prism
diopters
6.0 mm OU/25-30 prism diopters
7.0 mm OU/30-40 prism diopters
8.0 mm OU/40-50 prism diopters
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