Deep brain stimulation and eye movements

Deep brain stimulation (DBS) has been most widely used in the management of movement disorders, but more recently to treat a growing number of neurological and psychiatric conditions. It is know to have a variety of effects upon oculomotor function, depending not only on the location of the stimulation, but also the underlying pathology being treated. Understanding how DBS affects eye movements is important, given the widespread nature of eye movement control and its inevitable overlap with many of the networks targeted by the stimulation. Moreover, it can also offer additional mechanistic insights into neural circuits involved in complex eye movement control. Here, we discuss the application of DBS treatment across different diseases and explore how distinct stimulation locations interfere with known eye movement circuits and the ensuing oculomotor and visual effects it can produce. We also discuss more experimental DBS targets and its effects on ocular motility, as well as discussing unilateral versus bilateral deep brain stimulation and possible hemispheric asymmetry in relation to eye movement control. Contradictory findings across studies reporting DBS effects on eye movements likely relate to differences in the methodological approaches used, levodopa medication status, as well as possible variability in DBS electrode placement. We highlight the need for further research with less common DBS targets on the possible effects upon eye movements.