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BITEMPORAL
HETERONYMUSHEMIANOPIA
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CONTENTS:
Definition
Pathophysiology :
>Visual Pathways
>Visual Fields
Etymology
Causes
Diagnosis:
>Perimetry
>Confrontation testing
>Relation with underlying diseases
Treatment
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DEFINITION:
Bitemporal heteronymus hemianopia is a type of a
partial blindness where vision is missing in the
OUTER HALF or the temporal half of both the right
and left visual fields.
Hemi-anopia means the absence of vision in half of
the visual field of one eye.
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PATHOPHYSIOLOGY
VISUAL PATHWAYS:
A normal visual pathway has the following components:
o Retina
o Optic nerves
o Optic chiasm: where optic nerve fibres from thenasal hemiretina of both sides decussate and pass to
the opposite optic tract.
o Optic tracts
o LGNo Optic Radiation or geniculocalcarine tract
o Primary Visual Cortex or BrodmannsArea 17
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In bitemporal
hemianopia, the lesionor damage occurs in
the region of OPTIC
CHIASM.
*(labelled B)*
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VISUAL FIELDS:
The field of vision is the visual area seen by an eyeat a given instant.
>The area seen to the nasal side is called the nasal
field of division.
>The area seen to the lateral side is called thetemporal field of vision.
>>In this disease, the nasal half of each retina is
blinded which means the person is blind in the
temporal field of vision for each eye because theimage of the field of vision is inverted on the retina by
the OPTICAL SYSTEM of the eye.
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Paris as seen with normal eyes.
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Paris as seen with bitemporal heteronymus
hemianopia.
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ETYMOLOGY
bi-: involves both left and right visual fields
temporal: involves the temporal visual field
hemi-: involves half of each visual field
anopsia: blindness (formed by an, no + opsis,vision)
Why called heteronymusalthough both sidedtemporal visual fields are involved?
The word heteronymus/homonymus hemianopia is
used for the LEFT OR RIGHT sides of visual fields ofboth eyes.
Since, temporal side of right eye=right
temporal side of left eye= left ; so hetero.
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CAUSES
Tumors located at the mid-optic chiasm.
Pituitary Gland tumors:
They press upwards from the sella turcica (bony
border) on the bottom of the optic chiasm. Tumors include
Adenomas
Craniopharyngiomas
Aneurysm in the anterior communicating artery
which passes superior to the chiasm.
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Pituitary tumor causing lesion.
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DIAGNOSIS
PERIMETRY:
>It is a procedure in which the visual field of the
subject is found exactly and drawn on a chart.
>Subjects look at a central spot.>A small dot of light or an object is moved in the field
of vision.
>Subject tells whether he can see the object or not
and a graph is plotted in this way.>Digital perimeters are available now-a-days.
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COMPUTERIZEDANDANTIQUEPERIMETERS
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CONFRONTATION TESTING:
It is the bedside method of determining the visual
fields.
The doctor and patient are focussed on each otherand eye to eye.
The doctor makes sure whether the finger in his
visual field is also in the patients field of vision or
not.
Flicks his fingers or shows a number to count.
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RELATION WITH PITUITARY TUMOR:
When there is pituitary tumor as the underlying
cause, as it is most common, the levels of varioushormones in the body are upset.
Eg, TSH, T3, T4, Prolactin, etc.
Therefore, blood levels of these hormones are alsodetermined.
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CUREANDTREATMENT
There is usually no cure for hemianopias, but insome cases surgical procedure for removingpituitary tumor can be done.
Treatments include:
>Research>Goggles
> Audiovisual Stimulation Training
>Explorative Saccade Training
>Optical Visual Span Expanders>Visual Restoration Therapy
Most doctors recommend the uses of a combinationof these treatments.
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