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Fatema Ghasia, Aasef Shaikh, Mark Walker; Mechanisms of Pattern Strabismus: role of supra-nuclear neural circuits versus peripheral eye plant. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2571. doi: https://doi.org/.
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The purpose of this study was to quantitatively study eye movement and vestibular function in patients with pattern strabismus. Our goal was to delineate the role of impaired central processing in supra-nuclear motion circuits versus abnormal static torsion resulting in altered direction of recti muscle pull.
Eye movements were measured using high-precision video-oculography (VOG) (Eyelink 1000, SR research) in subjects with infantile pattern strabismus (IPS n=3), late onset pattern strabismus (LPS n=2), infantile comitant strabismus (IS n=1), late onset comitant strabismus (LS n=4) and from healthy controls (C n=15). Horizontal and vertical eye positions were simultaneously recorded during fixation, saccades, step-ramp pursuit and vestibulo-ocular reflex (VOR). Static torsion was measuring with fundus photography.
Oculomotor responses in the plane orthogonal to desired movements (cross-coupled responses) were seen in patients with pattern strabismus. The cross-coupled response was larger in IPS than LPS. The cross-coupled responses were evident during saccades more than smooth pursuit but not during VOR. There was a greater amount of static torsion as measured by fundus photos in IPS compared to LPS. The amount of cross coupled responses in human pattern strabismics was smaller compared to non-human primates reared by alternate monocular occlusion.
Cross coupled responses were seen in pattern strabismics and its amplitude varied with different class of eye movements. Infantile onset pattern strabismus could be due to abnormal neural connections whereas late onset pattern strabismus or pattern strabismus in patients with craniofacial anomalies could be due to orbital pulley instability.
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