A diagnostic test to identify the fourth (IVth) cranial nerve (trochlear nerve) damage that results in the superior oblique palsy of the eye. It works by isolating the paretic extraocular muscle (particularly the IVth cranial nerve) and superior oblique muscle in acquired vertical double vision. The eye exam uses the cover-uncover test to measure deviation in different head positions.

Also Known As

  • Park's Three-Step Test
  • The Parks–Bielschowsky Three-Step Test
  • Bielschowsky Test