past papers PART 02 questions and answers OCULAR ANATOMY AND OCULAR PHYSIOLOGY

  OCULAR ANATOMY AND OCULAR PHYSIOLOGY

1. Visual pathway and lesions of the visual pathway.

Visual pathway

• Retina
• Optic nerve
• Optic chiasm 
• Optic tract
• Lateral geniculate nucleus
• Optic radiation
• Primary and secondary visual cortices

*This is the sensory organ of the eye contact pathway to the central nervous system part of the cerebral of the visual cortex. 

*This pathway consists of more parts namely the eye to the brain are... Retina, optic nerve, optic chiasm, optic tracks, lateral geniculate bodies, optic radiation, the visual cortex. 

*The Visual pathway is part of the central nervous system, retina embryological origin in the extension of die-Cephalon.

Lesions of the visual pathway.

meaning of lesions

*The visual pathway consists of structures that carry visual information from the retina to the brain. Lesions in that pathway cause a variety of visual field defects.

Causes

*Causes of optic nerve lesions include optic atrophy, optic neuropathy, head injury 

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
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
	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	Occipital 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