Before the Optic chiasm – The visual field loss is seen on the same (ipsilateral) side as the lesion.
Fig 1 – lesion of right optic nerve gives a Right Monocular loss – Can be caused by – trauma, Multiple sclerosis
Fig 2 – lesion at optic chiasm – Can be caused by a pituitary tumour, craniopharyngioma, suprasellar meningioma
After the optic chiasm – The visual loss is seen on the opposite (contralateral) side of the lesion because the optic nerves have already crossed over at the optic chiasm.
Fig 3 – lesion at the right optic tract gives a left homonymous hemianopia. Can be caused by vascular disease, head injury, cerebral tumour.
Each eye has a left and a right visual field. In a left homonymous hemianopia the left visual field of both the right eye and left eye is lost but the lesion is of the right optic tract.
Fig 4 – lesion at the left optic radiation gives a right upper homonymous quadrantanopia. Can be caused by stroke, Space occupying lesions
Each eye has a left and right visual field. In a right upper homonymous quadrantanopia the right visual field of both the right eye and left eye is lost. The lesion is of the left temporal radiation (remember that Temporal produces a Top quadrantanopia).
Fig 5 – lesion of the parietal radiation will result in a lower homonymous quadrantanopia.
Fig 6 – Lesion at the right occipital lobe/pole. Gives a left homonymous hemianopia with macular/ central vision sparring. Can be caused by stroke in posterior circulation
Quick Summary Table
Loss of vision in one eye
Ipsilateral Optic Nerve
Left homonymous hemianopia
Right optic tract / radiation
Right homonymous hemianopia
Left optic tract / radiation
Contralateral optic radiation