Fourth nerve palsy with monovision.
The fourth cranial nerve is the most vulnerable cranial nerve. Its damage gives rise to a vertical ocular deviation and usually the patient comes with a right head-tilt. The Parks-Bielschowsky three-step test is a simple and useful test for identifying the paretic extraocular muscle, giving rise to such a vertical ocular deviation. A case of long-standing fourth nerve palsy in a 45-year-old woman is reported. Monovision spectacles were prescribed to give the patient satisfactory distant and near vision.
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