Convergence-retraction nystagmus does not meet the true definition of nystagmus because it lacks slow phases. This condition results from co-contraction of the extraocular muscles on attempted upgaze. The medial rectus muscles are the most powerful of the extraocular muscles, and their contraction produces convergent movements even when all other extraocular muscles are contracting. The co-contraction of all extraocular muscles causes retraction of the globe into the orbit. Convergence-retraction nystagmus localizes the disease process to the dorsal midbrain and is part of dorsal midbrain syndrome (see Chapter 8, Fig 8-5); therefore, this “nystagmus” is often associated with paresis of upgaze, pupillary light–near dissociation, skew deviation, and bilateral eyelid retraction (Collier sign). Convergence-retraction nystagmus is best demonstrated by having the patient attempt an upward saccade elicited on command or by following a downward-rotating OKN drum.
Excerpted from BCSC 2020-2021 series: Section 5 - Neuro-Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.