The misclassification of blinks as saccades: Implications for investigations of eye movement dysfunction in schizophrenia

It is important to have a simple, accurate method for recording eye movemen ts. Of the two popular approaches commonly adopted, electro-oculography (EO G) and infrared oculography (IROG), IROG is often accepted as the more accu rate, and it is the method that is currently used most frequently to examin e eye movements in schizophrenia. This study investigated whether the miscl assification of blinks as saccades affects saccade rates when the presence of a blink is determined using only IROG recordings of eye position. Both v ertical electro-oculography (VEOG), which can be used to objectively identi fy blinks, and IROG were recorded while 17 schizophrenia patients and 19 he althy controls were presented with sinusoidal stimuli. Of the blinks identi fied with the VEOG for the total group of participants, a substantial numbe r (37%) were misclassified as catch-up and anticipator), saccades when only the IROG was used. Furthermore, in the schizophrenia group, but not in the healthy control group, the use of the IROG led to a significant misclassif ication of blinks as anticipatory saccades. Therefore, when IROG alone is u sed to identify blinks, the misclassification of blinks as saccades is like ly to introduce measurement error into estimates of saccade rates, particul arly estimates of anticipatory saccade rates in schizophrenia patients.