Impaired saccadic eye movements on stationary targets in patients with schizophrenia spectrum disorder

This study examined tracking eye movements on predetermined stationary targets in patients with schizophrenia spectrum disorder. The targets were 8 black points or 8 arabic-numbered points placed on the circumference of a circle. Self-paced eye movements during clockwise tracking of these points by 23 patients and 23 normal controls were recorded using an infrared eye-mark recorder. Eye movements were analyzed at two settings: firstly, when fixation point was defined as a point at which a gaze was held for at least 200-ms; and secondly, when held for at least 100-ms. The results indicated that at the 200-ms setting schizophrenic patients track with significantly fewer correct scores and more deviant scores than controls under black-point conditions. At the 100-ms setting, however, the correct scores of patients were not significantly different from those of controls, although patients displayed more aberrant paths than controls. The superfluous fixations in the patients improved significantly under numbered-point conditions, but patients still achieved lower correct scores than controls. Four of the 23 patients exhibited centering (aberrant path directed toward the center point), suggesting immature control of eye movements under black-point conditions, but not numbered-point conditions. These results suggest that some schizophrenic patients viewed the targets too quickly, and that they have impaired directed attention, which can be improved by cues, and may have impaired preprogramming of eye movements, which is not improved by external cues.