Voluntary saccade control is poorly developed at the age of 8 years (Fischer et al., Brain Res., 754: 285-297). Up to 50% of dyslexic children exhibit a developmental deficit in producing voluntary saccades as tested by an antisaccade gap task (Biscaldi et al., Neuropsychologia, 36: 1189-1202). ADHD children, mostly boys, often also have difficulties in acquiring reading and spelling skills. Many of them are treated with Ritalin. We measured the eye movements of 24 boys (age 10 - 15; mean = 12 y) before and after the use of Ritalin using a prosaccade overlap task and an antisaccade gap task. For control we used the data of 24 normally developed age-matched boys. For analysis the variables extracted from the data were classified as F-variables that describe the quality of fixation or as A-variables describing the voluntary component (Fischer et al., Brain Res Protocols, 2: 47-52). Both the test and the control data were then individually compared with those of a large reference group (N = 94) of normal children subdivided into 3 age groups. For each child we counted the number of F- and A-variables that were off-limits by more than 2 standard deviations.

Before taking Ritalin the number of off-limits A-variables was significantly higher in the test as compared with the control group. Ritalin reduced this number to almost the value of the controls. The number of off-limits F-variables, by contrast, was not significantly different and did not allow to differentiate the ADHD group from the control.

This study shows that in ADHD the voluntary saccade control component is not fully developed while reflexive saccades are normal. Ritalin reduces this deficit for the duration of its effectiveness. This observation is in line with the hypothesis that in ADHD frontal lobe functions are affected. From preliminary observations we know that daily practice can reduce the problems in voluntary saccade control not only in dyslexia but also for children with ADHD. Unfortunately, not all of the present subjects were tested for dyslexia.