Question 7.2

7.2 The following assessment was made on the visual field testing of a patient who presented with impaired vision.

(The darkened halves of the fields indicate the area of impaired vision).

a) What does the visual field testing indicate?

b) List 3 likely anatomical sites of lesion which may result in this visual defect.

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College Answer

a) What does the visual field testing indicate?
Rt. homonymous hemianopia

b) List 3 likely anatomical sites of lesion which may result in this visual defect.

Left optic tract
Left optic radiation
Left occipital lobe

Discussion

The localisation of visual field defects lends itself especially well to a massive insane-looking eyeball diagram, which I have put together many years ago in med school.

For detailed references, one can be directed to Chapter 116 by R.H Spector from Clinical Methods(1990), or "Topical diagnosis of chiasmal and retrochiasmal disorders" by Levin, from Walsh and Hoyt clinical neuro-ophthalmology, 6th ed.

Alternatively, one can explore this table cut-and-pasted from the Required Reading section (Visual fields and lesions of the visual pathways). As you can plainly see, one can put "tumour" down as a cause for pretty much any of these

Lesions of the Visual Pathwas, with Clinical Correlations
Lesion	Localisation	Causes
Big blind spot	Retina Optic nerve head Optic nerve	Optic neuritis Optic disk oedema (papilloedema) Choreoretinitis
Tunnel vision	Optic nerve head Optic nerve	Papilloedema Optic neuritis involving external fibers
Central scotoma	Optic nerve	Papilloedema Optic neuritis involving internal fibers
Unilateral blindness	Whole eye Optic nerve (whole)	Involvement of the whole retina Involvement of whole optic nerve: Retinal artery occlusion Retinal vein occlusion Neuroma Trauma Tumour (retinublastoma)
Bitemporal hemianopia	Optic chiasm	Pituitary adenoma Glioma Medial sphenoid ridge meningioma Aneurysms near the sella turcica Ectatic ACA
Homonymous hemianopia	Optic Tract	Anterior choroidal artery infarction Multiple sclerosis (or other demyelinating disease) Trauma Tumour
	Lateral geniculate nucleus	Richly vascularised; difficult to take out with one ischaemic stroke: anterior choroidal artery and lateral geniculate artery are both involved in blood supply. Pontine myelinolysis Trauma Syphilitic arteritis Tumour
	Optic radiation	Internal capsule stroke (eg. basilar artery) MCA stroke (lenticulostriate arteries) Haemorrhage Tumour
	Occipial lobe (extensive)	PCA stroke PRES (posterior reversible encephalopathy) Trauma Tumour
Homonymous hemianopia with macular sparing	Occipial lobe (limited)	PCA stroke PRES (posterior reversible encephalopathy) Trauma Tumour
Superior quadrantinopia	Temporal fascicle of optic radiation	Anterior temporal lobe damage: less likely to be vascular. Infection (eg. mastoiditis leading to brain abscess) Trauma (eg. SDH) Tumour
Inferior quadrantinopia	Parital fascicle of optic radiation	Parietal lobe stroke (PCA) Haemorrhage Tumour

References

Levin, Leonard A. "Topical diagnosis of chiasmal and retrochiasmal disorders."Walsh and Hoyt clinical neuro-ophthalmology, 6th ed. Baltimore: Williams & Wilkins (2005): 503-573.

Robert H. Spector. "Visual Fields." (1990). Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition.

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Question 7.2

College Answer

Discussion

Lesion

Localisation

Causes

References