Average data for controls, strabismic amblyopes, and nonstrabismic amblyopes are shown in
Figure 7. While controls showed very little suppression on average, observers with amblyopia exhibited suppression throughout the whole 20° field. This suppression was particularly pronounced within the central 6° of the test stimulus. A mixed ANOVA with factors of eccentricity (five levels: 0–2, 2–4, 4–6, 6–8, and 8–10) and group (strabismic amblyopes, nonstrabismic amblyopes, and controls) revealed a significant main effect of the group (F
2,21 = 13.549,
P < 0.001). Post hoc Bonferroni tests (corrected for multiple comparisons) revealed significant differences between controls and strabismic amblyopes (
P < 0.001) and between controls and nonstrabismic amblyopes (
P < 0.03). Strabismic and anisometropic amblyopes did not differ reliably from one another. There was also a significant main effect of eccentricity (F
4, 84 = 19.46,
P < 0.001), whereby suppression reduced with increasing eccentricity. There was a marginal interaction between group and eccentricity (F
8, 84 = 1.942,
P = 0.064), which was significant if the data for the strabismic and nonstrabismic amblyopes were pooled (F
4, 88 = 3.172,
P < 0.05). This indicates that the effect of eccentricity on the magnitude of suppression was more pronounced for amblyopes than for controls. Interestingly, we found reliable relationships between the magnitude of central suppression and the depth of amblyopia (
Fig. 8A). In addition, the strength of suppression in the central region of the stimulus was correlated with the strength of suppression in the peripheral regions of the stimulus (
Fig. 8B). It would appear, therefore, that the regional extent of suppression is related to the extent of monocular vision loss in the amblyopic eye.