Like horizontal deviations, vertical deviations can be paretic or non-paretic. Proper diagnosis of non-paretic deviations relies on history (infantile onset, prior surgery, trauma, etc.), and relevant systemic illness (thyroid eye disease [TED], etc.). The diagnosis of paretic deviations relies on the pattern of misalignment and ductions and versions. In general, the greatest deviation will be in the field of action of the paretic muscle, unless secondary changes have occurred in other muscles, e.g., contracture causing a spread of comitance. The Parks three-step test relies on this principle , taking the actions of the muscles on forced head tilt into account according to the teachings of Bielschowsky [1, 2]. The three-step test has become the mainstay in diagnosing vertical strabismus. However, it is only designed to tell which of the eight cyclovertical muscles might be palsied. It does not tell if you are in fact dealing with a palsy of one cyclovertical muscle. And when patient presents to you, it is your job to determine whether or not that is what your patient has. There are numerous causes of vertical strabismus for which the three-step test may incorrectly implicate one muscle as being paretic.
Anti-elevation syndrome Brown syndrome Cranioacial syndromes Dissociated vertical divergence (DVD): Definition, Pathophysiology, Treatment Duane syndrome Inferior oblique (IO) anterior transpositions Inferior oblique (IO) overaction IO palsy Myasthenia Overdepression in adduction Overelevation in adduction Prism under cover test Pulley abnormalities Restriction Skew Superior oblique (SO) Superior oblique palsy (SOP) SO incarceration SO overaction Three Step Test: Errors in Torsion-objective Torsion-subjective Vertical rectus overaction Vertical rectus palsy Vertical strabismus: Diagnosis, Measurement of
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