Is eye tracking dysfunction specific to schizophrenia?

Based on eye tracking studies in psychiatric patients, normal controls, and first-degree relatives of patients, Holzman, Proctor, and Levy et al. (1974) state that eye tracking dysfunction (ETD) is specific to schizophrenia and may be a genetic marker of that disorder. A review of numerous subsequent studies, however, suggests that ETD is not specific to schizophrenia, but is restricted to functional psychosis. Evidence that ETD is a genetic marker of functional psychosis is, as yet, inconclusive.