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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
INTRODUCTION
Dissociated strabismus represents a
challenge for diagnosis and surgical treatment.
It is commonly found in patients with early
onset strabismus and profound sensorial
anomalies.
Diagnosis is not easy because the
movement is slow and needs a more
prolonged occlusion to appear; the amount of
deviation is variable, intermittent and depends
on attention. Besides, these patients usually
show horizontal, vertical and torsional
movements when performing the cover test
and the amount of deviation is different when
fixing with each eye. They also have head tilts
and associated oblique muscles dysfunctions
in many cases.
Therefore, surgical treatment of patients
with DVD (Dissociated Vertical Deviation)
and DHD (Dissociatd Horizontal Deviation)
requires a specific surgical approach. Longterm
surgical results and recommendations for
these cases remain sparse in literature.
The purpose of this article is to report
the clinical characteristics and the surgical
outcomes of 20 patients with DVD and DHD
who underwent surgery between 2000 and
2007 and have a mean of 35 months of postsurgical
follow up.
PATIENTS AND METHODS
Retrospective record review of patients
operated on for DVD and DHD between 2000
and 2007. (See Table 1, next page.)
The diagnosis of DHD was made
according to the detection of a different
horizontal deviation when fixing with each
eye during cover testing; unrelated to
accommodation, muscle weakness or
restriction which can induce a primary and
secondary deviation.
The horizontal deviation cannot be
neutralized through the classical prism and
alternating cover test. Alternate cover testing
must be performed slowly allowing the nonfixing
eye time for the slow drift to fully
manifest. It is necessary to make the right eye
fixate first and neutralize with prism the left
eye deviation and then let the left eye fixate
and neutralize the right eye deviation.
Measuring horizontal and vertical
dissociated deviations is complicated because
we need to superimpose horizontal and
vertical prisms over each eye. In addition, it is
necessary to measure DVD and DHD with
each eye fixating in all gaze positions
(including head tilts) in order to have the
necessary panorama to choose the best
surgical procedure for each case.
The Reversed Fixation Test (RFT) had
been performed in 7 patients only before the
surgery. During this test, the patient was asked
to fixate through the prism that neutralized the
deviation of the non-fixing eye and then the
occluder was shifted to the fixing eye while
being observed for any refixation movement
when the cover test was performed. The test is
positive when we can observe a refixation
movement which can be measured placing
prisms in front of this fixing eye.
DHD is often observed to be larger with
visual inattention than when the prism
measurements are made and the eye position
under general anesthesia usually shows
greater deviation than the measured angle in
the awake state.
The following data were obtained: 1)
age of strabismus onset 2) sex 3) history of