visual field defect,...where is the lesion?

click on this link for visual field simulator.

be confident of detecting the common field defects in clinical practice:

1-Homonymous hemianopia

2-Bitemporal hemianopia

3-upper & lower quadrantic hemianopia

4-Scotoma

Homonymous Hemianopia:

the patient does not see one half of the visual field-left or right.

in left homonymous hemianopia the patient does not see the left half of the visual field.

the lesions producing homonymous hemianopia are either in the optic tract or radiation.

optic tract-->incongruous hemianopia

optic radiation -->congruous hemianopia

optic tract lesions may produced by : pituitary tumour, craniopharyngioma or meningioma.

opyic radiation lesions are usually due to tumor or infarction inthe middle cerebral artery territory.

visual cortex lesions produce a mcular sparing homonymous hemianopia and may occure with migrane and posterior cerebral ischemia.

Temporal Hemiaopia:

may be unilateral or bilateral.

usually due to chiasmatic compression.

when there is compression from above (craniopharyngioma) the lower fields are affected first and more.

Quadrantic field defects:

this is due to involvement of fibres sweeping from lateral geniculate body to the visual cortex.

the upper fibres sweep through the parietal lobe and lower fiber through the temporal lobe.

temporal lobe lesion--->upper quadrantanopia

pareietal lobe lesion--->lower quadrantanopia

Central Scotoma:

island of loss of vision surrounded by normal visual field.

common causes:optic nuritis and optic atrophy.