• Disordered smooth-pursuit eye movements occur in a high percentage of schizophrenic patients and their first-degree relatives. A test of the hypothesis that these disorders represent a genetic indicator of schizophrenia was undertaken by testing pursuit eye movements in a sample of monozygotic and dizygotic twins discordant for clinical schizophrenia. Deviant eye tracking is significantly concordant within monozygotic twin pairs, and less so within dizygotic twin pairs discordant for schizophrenia. A genetic interpretation is consistent with these results.
Holzman PS, Kringlen E, Levy DL, Proctor LR, Haberman SJ, Yasillo NJ. Abnormal-Pursuit Eye Movements in SchizophreniaEvidence for a Genetic Indicator. Arch Gen Psychiatry. 1977;34(7):802-805. doi:10.1001/archpsyc.1977.01770190064005