Left optic tract
Loss of vision in the right halves of both eyes indicates right homonymous hemianopia. The visual pathway anatomy: fibers from the temporal retina (representing nasal/contralateral visual field) remain ipsilateral, while fibers from nasal retina (representing temporal/ipsilateral visual field) cross at the optic chiasma. A lesion of the LEFT optic tract will cause loss of vision in the RIGHT visual field of both eyes (right homonymous hemianopia), as it affects fibers from the left temporal retina and right nasal retina.