Figure 3.

Diffusion tensor imaging (DTI) and tractography results of AC2 and 30 controls. A) ROIs and estimated fiber bundles superimposed on the T1 weighted axial slice, viewed from below. Estimates of the right (red) and left (blue) optic tracts; the right (pink) and left (purple) optic radiations; the right (dark red) and left (dark blue) occipital callosal fibers. Yellow spheres represent the optic chiasm (large anterior) LGN’s (small in the middle) and Calcarine sulcus (posterior) regions of interest. (B) Scatter plot of the radial and longitudinal diffusivities of the optic tract, optic radiation and occipital callosal fiber groups (see color legend on the right). The 2 standard deviation covariance ellipsoid of 30 normally sighted subjects is drawn for each fiber group. The black stars represent the averaged right and left diffusivity values for each fiber group in the achiasmic subject which are within the range of control subjects. (C) The location of the occipital callosal fibers in the plane of the corpus callosum. (D) Scatter plot of the cross-sectional area of the occipital callosal fiber group in relation to the cross-sectional area of the entire corpus callosum. The cross-sectional area of achiasmic occipital callosal fiber group (purple star) is small compared to the controls (grey diamonds); however, the overall size of AC2’s corpus callosum is small too.