Symptom reduction in acutely ill schizophrenia patients treated with 15 mg of haloperidol
was associated with a detrimental effect (increased error rate) on a voluntary eye movement
task in those patients who were initially cognitively intact. This decline in performance was
also reflected on the Word-Color subscale scores of the Stroop Task. Such deterioration was
not evident in those schizophrenia patients who were initially cognitively-impaired prior to
haloperidol administration. This suggests that the prior discrepant findings in the literature
about the effect of haloperidol on eye movements may simply be due to heterogeneity in the
schizophrenia population. Of significant clinical importance, this study indicated (1)
changes in symptom reduction may not parallel changes in cognitive performance, (2)
voluntary eye movements may be a sensitive measure of cognitive change and (3)
schizophrenia patients may have differential cognitive responses to typical antipsychotics
depending on whether their cognition is initially intact or impaired. These concepts are
crucial to optimal evaluation and treatment of schizophrenia patients given cognition is the
strongest predictor of long-term prognosis.