It is important to have a simple, accurate method for recording
eye movements. Of the two popular approaches commonly adopted,
electro-oculography (EOG) and infrared oculography (IROG), IROG
is often accepted as the more accurate, and it is the method
that is currently used most frequently to examine eye movements
in schizophrenia. This study investigated whether the
misclassification of blinks as saccades affects saccade rates
when the presence of a blink is determined using only IROG
recordings of eye position. Both vertical electro-oculography
(VEOG), which can be used to objectively identify blinks, and
IROG were recorded while 17 schizophrenia patients and 19 healthy
controls were presented with sinusoidal stimuli. Of the blinks
identified with the VEOG for the total group of participants,
a substantial number (37%) were misclassified as catch-up and
anticipatory 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 misclassification of
blinks as anticipatory saccades. Therefore, when IROG alone
is used to identify blinks, the misclassification of blinks
as saccades is likely to introduce measurement error into estimates
of saccade rates, particularly estimates of anticipatory saccade
rates in schizophrenia patients.