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Biol Psychiatry. 2012 May 22;
Authors: Benson PJ, Beedie SA, Shephard E, Giegling I, Rujescu D, St Clair D
Abstract
BACKGROUND: We have investigated which eye-movement tests alone and combined can best discriminate schizophrenia cases from control subjects and their predictive validity.
METHODS: A training set of 88 schizophrenia cases and 88 controls had a range of eye movements recorded; the predictive validity of the tests was then examined on eye-movement data from 34 9-month retest cases and controls, and from 36 novel schizophrenia cases and 52 control subjects. Eye movements were recorded during smooth pursuit, fixation stability, and free-viewing tasks. Group differences on performance measures were examined by univariate and multivariate analyses. Model fitting was used to compare regression, boosted tree, and probabilistic neural network approaches.
RESULTS: As a group, schizophrenia cases differed from control subjects on almost all eye-movement tests, including horizontal and Lissajous pursuit, visual scanpath, and fixation stability; fixation dispersal during free viewing was the best single discriminator. Effects were stable over time, and independent of sex, medication, or cigarette smoking. A boosted tree model achieved perfect separation of the 88 training cases from 88 control subjects; its predictive validity on retest assessments and novel cases and control subjects was 87.8%. However,when we examined the whole data set of 298 assessments, a cross-validated probabilistic neural network model was superior and could discriminate all cases from controls with near perfect accuracy at 98.3%.
CONCLUSIONS: Simple viewing patterns can detect eye-movement abnormalities that can discriminate schizophrenia cases from control subjects with exceptional accuracy.
PMID: 22621999
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The problem is translating this data from a group study into a reliable screen for an individual patient. And what about abnormal eye movement results from other illnesses. Is there a group of eye movement tests that can distinguish schizophrenia from other causes of eye movement abnormalities? Given the large overlap between schizphrenia and mood disorders, what about eye movement tests that can distinguish paranoid schizophrenia – which I consider a mood disorder plus psychosis given the underlying pathophysiology – from generalized anxiety disorder or bipolar disorder.