Convergence paralysis after lesions of the cerebellar peduncles

We studied vergence eye movements in a patient with limited hemorrhage affecting the right cerebellar peduncles and the hemisphere. The patient showed exotropia of 30 prism dptr during near vision. Some vergence paradigms were investigated in this patient. We studied fusional vergence evoked by placing a wedge prism before one eye. Accommodative vergence was studied by blur stimulus using a servocontrolled optometer. Lens accommodation was also recorded during blur stimulus. Although accommodative responses were normal, accommodative vergence was almost absent as well as fusional convergence in this patient. It has previously been reported that the cerebellum has a role in the control of vergence in the monkey. Our data suggest that the human cerebellum also relates to the control of vergence.