Altered performance on an ocular fixation task in attention-deficit/hyperactivity disorder

Background: Attention-deficit/hyperactivity disorder (ADHD) is a common psychiatric disorder without validated objective markers. Eye movement studies may be useful in providing objective criteria for characterizing the disorder. Methods: We compared 53 children (29 girls) with ADHD to 44 healthy control children (18 girls) on a 21-sec fixation task. Large saccades (> 4°) away from the fixation point were analyzed. Results: Children with ADHD made more large saccades that interrupted fixation than did control children (p = .001). Mean scores of the ADHD group did not change significantly with subsequent retesting on placebo (p = .11); however, there was poor intrasubject correlation (r = .16). Conclusions: Both boys and girls with ADHD made significantly more intrusive saccades during fixation than did control subjects, possibly reflecting intrinsic neurologic dysfunction; however, a probable “floor effect” obviates conclusions about the reliability of this measure.