Convergence

Convergence: instruct the patient to focus on their thumb held at arm's length, and slowly move their thumb towards their nose. This may bring out or cause reversal of vertical nystagmus (e.g., transition from upbeat to downbeat nystagmus in Wernicke's encephalopathy [see example of transition from DBN to UBN with convergence in brainstem encephalitis - https://collections.lib.utah.edu/ark:/87278/s6bg75c3]; see example of increased ocular flutter and UBN with convergence with a posterior fossa tumor - https://collections.lib.utah.edu/ark:/87278/s6867r9v), may exaggerate other acquired forms of nystagmus, and damp congenital/infantile nystagmus. If the patient complains of binocular symptoms or double vision while reading and near viewing and the patient has a near point of convergence >10 cm, think about convergence insufficiency (particularly with parkinsonism [https://collections.lib.utah.edu/details?id=1253803] or TBI/concussion).