Results from the symptom questionnaire. Each panel shows the results from one question (Figure 4, left). From left to right, the questions concern eye tiredness, vision clarity, neck and backache, eyestrain, and headache. The abscissa in each panel is modulation frequency, and the ordinate is symptom rating (larger numbers indicate more severe symptoms). The green circles are for the natural-viewing condition and the red diamonds are for the S3D-viewing condition. Each data point is the mean of 31 subjects’ data. Error bars represent standard errors. Double asterisks indicate a significant difference (p<0.05).