Speedy assessment of visual acuity in amblyopia by the evoked potential method.

As an objective means of assessing visual acuity in young children and of monitoring acuity changes during occlusion therapy, the value of conventional evoked potential recording is restricted by lengthiness and by variability. This article describes one way of circumventing these disadvantages. A graph of evoked potential amplitude versus stimulus check size was continuously plotted while the child viewed a rapidly-oscillating chequerboard pattern whose check size was slowly zoomed up and down. Empirically, the shape of this graph gives an index of acuity and of the acuity difference between the amblyopic and fellow eye. The child's attention could be held for the 2-4 min required by superposing a movie cartoon on the chequerboard pattern, though the movie had a negligible effect on the chequerboard evoked potentials. The briefness of the procedure had the additional advantage of reducing variability.