Quantitative assessment of eye movements using a binocular paradigm: comparison among amblyopic, cured amblyopic and normal children

Background: To investigate the fixation and saccade functions in children with amblyopia and cured amblyopia by a binocular eye-tracking paradigm. Methods: Eye movements of 135 pediatric subjects, including 45 amblyopic children, 45 cured amblyopic children and 45 age-similar normal controls, were recorded under binocular viewing. The deviation (degree) between fixation positions and the visual targets along horizontal or vertical axis was recorded as the mean from both eyes. Deviations were compared across three groups and between each two groups. Results: Main outcome measures included deviations along horizontal and vertical axes in the circular fixation test (Fix-X, Fix-Y) and horizontal saccade test (Sac-X, Sac-Y). All four deviations were significantly larger in the amblyopia group compared to the other two groups, indicating fixation and saccade deficits. However, there was no significant difference in deviations between cured amblyopic children and normal controls. In the amblyopia group, four deviations were similar across subgroups of varying amblyopia severity. Larger deviations were related to younger age and poor visual acuity overall. Conclusion: Amblyopic children have poor fixation and saccade functions, while cured amblyopic children seem to restore the functions. This paradigm provides a promising technique to evaluate and follow up the functional recovery.