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Alternate cover test reveals a right hyperphoria and exophoria

Legend: This video of the same patient as in Supplemental Digital Content 8-1 shows an exotropia (reflective of left medial rectus weakness) and a left hypotropia (reflective of left superior rectus and inferior oblique weakness). Notice how the movements of the right eye are greater than the left eye during the test, even though it is not the paretic eye; the left eye is unable to move because of paresis. The deviation of the right eye (there is both an exotropia and hypertropia) is an example of a secondary deviation and results from the Hering law of equal innervation, which states that an equal force is provided to each eye.

Duration: 00:14

Associated with: August 2014, Volume 20, Issue 4;

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