Impaired or absent optokinetic nystagmus was observed significantly more frequently among patients with tardive dyskinesia than among nondyskinetic control subjects. In view of known abnormal ocular motor responses in patients with Parkinson disease and Huntington chorea, this finding may be a consequence of chronic chemical denervation of dopamine receptors in the striatum.
Lipper S. Impairment of Optokinetic Nystagmus in Patients With Tardive Dyskinesia. Arch Gen Psychiatry. 1973;28(3):331-333. doi:10.1001/archpsyc.1973.01750330031005