Correspondence - ICO Library

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Binocular Vision & Inferior Oblique Muscle Palsy with ‘Paradoxical’ V-Pattern Strabismus FIRST Quarter of 2011
Strabology Quarterly© E. Khawam, MD and D. Fahed, MD Volume 26 (No.1)
A Medical Scientific e-Periodical Pages 51-60
On external examination, the patient showed
a face turn to the left (Figure 5, below) and, at
times, a head tilt to the right shoulder.
The presence of a habitual head tilt, the
positive BHTT, the marked overaction of the
antagonist SO muscle, and the improvement
of elevation action of the IO muscle in
adduction by duction compared to version all
rule out Brown Syndrome (6). Forced duction
test could not be done since the patient failed
to return to our clinic as repeatedly requested
and was therefore “lost to follow up”.
A pseudo-V-pattern can occur if glasses
are not worn, because correction reduces the
deviation by an unequal amount in elevation,
primary position, and depression. To avoid it,
all our measurements were done with full
optical correction at distance and near (11).
A pseudo-V-pattern, as well as failure
to diagnose a clinically significant A-pattern
can be seen if accommodation is not
controlled during measurements of the A- and
V-patterns. That is due to the un-naturalness
t o t h e s u b j e c t t o e x e r t
accommodative effort in upward
gaze, consequently resulting in a
de-crease of accommodative convergence
in that position (11). That
was avoided by measuring the A-
and V-patterns at the fixation
distance of 6 meters.
DISCUSSION
A- and V-patterns manifested
by a horizontal change of
binocular alignment of the eyes
from upgaze to downgaze are
common (12). V-patterns are most
commonly associated with IO
muscle overaction and A-patterns
with SO muscle overaction (13).
Figure 5 (Khawam & Fahed):
Our patient showing a 20 degree face turn.
The principles advanced to
explain the cause of A- and V-
patterns are discussed in the
literature by Costenbader (12) and
Parks (13). However, “paradoxical”
A- and V-patterns to the
horizontal deviation are rare.
There are few illustrating reports
in the literature: