Convergence-retraction nystagmus (CRN) is an eye movement abnormality in which, when a patient attempts to look upward, the eyes instead point inward (converge) or move backward (retract into the orbit) slightly. This usually begins abruptly in adulthood; less commonly, it comes on gradually or begins in childhood. There are several potential underlying causes. A patient with CRN will usually get brain imaging (typically an MRI). The treatment and prognosis depend on the underlying cause.