Incorrect

Incorrect

Correct! These visual field defects have the following distinctive features: they are wedge-shaped in both eyes with one border aligned to the vertical meridian, the other extending out radially. You can see why they are called “homonymous hemianopic pie-in-the-sky” defects. They represent damage to the post-geniculate axons that curve around the anterior portion of the temporal horn of the lateral ventricle (“Meyer’s loop”) before joining up with the remaining axons of the optic radiations.

If these defects had had borders aligned to the horizontal meridian, you would have called them “homonymous quadrantanopias,” and properly blamed the damage on a visual cortex lesion. In this case, the patient had undergone laser ablation of the anterior temporal lobe for intractable seizures. By the way, ablation extending beyond 4cm posterior to the anterior temporal tip is bound to cause such “pie-in-the-sky” visual field defects. The good news is that patients will not be impaired by them (or even notice them) unless the ablation extends back more than 6cm from the anterior temporal tip, in which case the root of the optic radiations may be damaged and the radial border of the homonymous defects will stretch closer to the horizontal meridian. Procedures in this region can also damage the anterior choroidal artery and its supply of the optic tract.