In a case of left Homonymous Hemianopsia, where is the lesion?

Left Homonymous Hemianopsia is a visual field loss that affects the same side (left side) of the visual field in both eyes. This condition results from a lesion that impacts the pathway of visual information from the visual field to the brain.

When considering the visual pathways, the fibers in the optic tract carry information from the retina to the lateral geniculate nucleus of the thalamus. Each optic tract contains fibers from the opposite visual field. Thus, a lesion in the right optic tract would disrupt the visual information coming from the left visual fields of both eyes, leading to left Homonymous Hemianopsia.

This is in contrast to lesions in the left optic nerve, which would cause vision loss in only the left eye, and lesions in the optic chiasm, which typically result in bitemporal hemianopsia, affecting peripheral vision in both eyes. A lesion in the left optic tract would produce right-sided visual field loss, which is not consistent with the presentation of left Homonymous Hemianopsia. Therefore, the location of the lesion leading to this specific visual field loss is indeed in the right optic tract.