Correspondence - ICO Library

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Binocular Vision & Diagnosis and Surgical Treatm ent of Dissociated Horizontal Deviation Strabism us FIRST Quarter of 2011
Strabology Quarterly© S. Gam io, M D Volum e 26 (No.1)
A M edical Scientific e-Periodical Pages 43-50
months (6 to 84 months).
The final binocular alignment and the
follow up time since the last surgery are
shown in Table 3, prior page.
DISCUSSION
DHD has become a more recognized
entity in the last few years and is usually
related to the horizontal deviation that is
associated to DVD in patients with early onset
strabismus history. (1-6) The main diagnostic
signs of DHD are the presence of horizontal
deviation (ET or XT) that changes with the
fixation of each eye, unrelated to different
accommodation due to anisometropia or
presence of primary and secondary deviation
due to weakness or restriction.
It is a slow and variable horizontal
movement, similar to the intermittent
hypertropia that characterizes DVD.
Commonly both conditions coexist; both are
variable and difficult to measure and are also
more prominent during inattention.
The Reversed Fixation Test was
proposed to diagnose dissociated strabismus.
It was first described by Mattheus and col.
(7)as a clinical tool to diagnose DVD and
later Graf applied it to DHD.(8-10)
Brodsky (11) found that 50% of his
patients with consecutive exotropia had DHD
as evidenced by a positive RFT. Seven of the
14 patients with DHD had a greater
exodeviation when fixating with the preferred
eye in Primary Position (PP). In our series, 8
patients had greater exodeviation when
fixating with the dominant eye, 4 patients had
greater esodeviation when fixating with the
non dominant eye and 2 cases had XT when
fixating with the dominant eye and ET when
fixating with the non-preferred eye. Five
patients had greater esotropia when fixing
with the dominant eye. (cases 6,13,16,19,20).
These findings seem to support his hypothesis
that the exodeviation is usually smaller with
the nonpreferred eye fixating.
Actually, patients with DVD and DHD
may also have horizontal and vertical nondissociated
deviations. If we perform RFT for
the vertical deviation alone we can still see the
horizontal movement of the eye that is not
neutralized with prisms. If we neutralize the
horizontal deviation first, the vertical
deviation we are measuring is not the vertical
deviation that we have in Primary Position
(PP). In certain cases, DVD is known to be
very asymmetric in lateral gazes, so if we are
performing RFT with a 25 pd base in prism in
front of the left eye, we are measuring the
right DVD in abduction, not in PP.
Examining the patient under general
anesthesia (GA) is extremely useful to decide
the amount of surgery to be performed. The
eye position under GA tends to show greater
exodeviation when the innervational forces
are abolished. The forced duction can reveal a
restriction and the spring back test can
determine a weakness in a previously recessed
medial rectus muscle.
In 1991, Wilson and McClatchey (12)
recommended graded unilateral lateral rectus
recession for the treatment of DHD and this
was the most common method to treat it
when surgery was indicated.
It was said that bilateral surgery is less
often required for DHD than for DVD.
However, DHD is almost always associated to
DVD. Therefore, bilateral surgery to treat both
is a good option in many patients. Wilson et al
(13) had reported their outcomes from
surgical treatment of 33 consecutive patients