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
Dr Tom Leach MBChB DCH EMCert(ACEM) currently works as a GP Registrar and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009.
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