Group and individual contrast discrimination thresholds for each condition are shown in
Figure 6. A 3 × 4 mixed ANOVA—(group: control, MO, or MA) × (conditions: black–dark gray, white–light gray, black–light gray, or white–dark gray)—was performed on the log contrast discrimination threshold data. There was a significant effect of stimulus type (
F3,159 = 54.21,
P < 0.001) but no main effect of group (
F2,53 = 1.60,
P = 0.21) or interaction between group and stimulus type (
F6,159 = 1.98,
P = 0.07). Tukey's post hoc tests showed that the contrast discrimination threshold for black–dark gray (type 1) was significantly smaller than for white–light gray (type 2;
P = 0.002; mean difference on log threshold = 0.08; 95% CI, 0.03–0.12;
dav = 0.42). The contrast discrimination threshold for white–light gray (type 2) was significantly smaller than for black–light gray (type 3;
P < 0.001; mean difference on log threshold = 0.13; 95% CI, 0.09–0.18;
dav = 0.76) and for white–dark gray (type 4;
P < 0.001; mean difference on log threshold = 0.15; 95% CI, 0.11–0.19;
dav = 0.88). The contrast discrimination thresholds for black–light gray (type 3) and white–dark gray (type 4) were not significantly different from each other (
P = 1). These results suggest that migraine or aura status did not affect contrast discrimination thresholds.