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-48- 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 TABLE 3: RESULTS: 20 Patients with DHD and DVD After Surgery performed. Legend:SR rec: Superior Rectus Recession; MR rec: Medial Rectus recession; w/adj sut: with adjustable sutures; IR rec: Inferior Rectus recession; LLR rec: Left Lateral rectus recession; SO tenec: Superior Oblique tenectomy, Bilat IOAT: Bilateral Inferior Oblique Anterior Transposition SO weak: Superior oblique weakening; DVD:Disociated Vertical Deviation; ET: esotropia, XT: exotropia ; hyper: hypertropia. Fix OD: Right eye is fixing Fix OS: left eye is fixing; ortho :Orthotropia; IO: Inferior Oblique ; SO:Superior Oblique
-49- 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
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