Optic atrophy and chiasm

Optic atrophy

Optic atrophy means disc pallor, from loss of axons, glial proliferation and decreased vascularity that follows many pathological processes, e.g. infarction of the nerve from thromboembolism or following papilloedema, inflammation (demyelinating optic neuritis in MS, syphilis, LHON), optic nerve compression, previous trauma, toxic and metabolic causes (vitamin B12 deficiency, quinine and methyl alcohol ingestion). Optic atrophy is described as consecutive or secondary when it follows papilloedema of any cause. The degree of visual loss depends upon underlying pathology.

Optic chiasm

Bitemporal hemianopic field are the typical defects when a mass compresses the chiasm. Common causes are:

pituitary neoplasm
meningioma
craniopharyngioma
secondary neoplasm.

In any case of bilateral visual loss, chiasmal compression must be considered.

Optic tract and optic radiation

Optic tract lesions (which are rare) cause field defects which are homonymous, hemianopic and often incomplete and incongruous. Optic radiation lesions cause homonymous quadrantanopic defects. Temporal lobe lesions (e.g. tumour or infarction) cause upper quadrantic defects, and parietal lobe, lower.

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Neurological examination

Optic nerve and visual system

Optic neuritis

Papilloedema

Pupil

Nervous System Disorders

Epilepsy

Cerebral stroke

Transient ischaemic attack


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