Seesaw Nystagmus Shown in 2 Half Cycles

This is a 5-year-old girl with congenital seesaw nystagmus due to achiasma. Achiasma is the absence of the optic chiasm when nasal optic nerve fibers fail to decussate to the contralateral hemisphere. As can be seen in this video, seesaw nystagmus is characterized by alternating vertical and torsional nystagmus in which 1 eye rises and intorts while the other falls and extorts. This is followed by reversal of the vertical and torsional components in the opposite eye. Click the Related Article link for full details.