EEG alpha rhythm amplitudes of six eccentrically fixating amblyopes between 8-39 years of age were studied during habitual fixation and central fixation with the amblyopic eye while the non-amblyopic eye was patched. Central fixation was achieved by utilizing an entopic phenomenon called Haidinger Brush and placing this brush-shaped image on a small letter. For each subject, habitual fixation of the amblyopic eye was considered the control, and attempting to centrally fixate with that eye was designated as the variable. The same procedure was repeated for the non-amblyopic eye of each subject. The latter was considered a second population, and the results were used to study the extent of psychological artifacts that could influence the results of this study. After one month of testing (up to 12 sessions for each subject) the amblyopic eye showed decreased amplitude of alpha rhythm when attempting to centrally fixate. However, the same result was obtained in the second population (the non-amblyopic eye) which suggests that some of the decrease in the amplitude may be the result of psychological factors such as motivation, anxiety and alertness while attending to a task.
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