Bitemporal Heteronymus Hemianopia

8/11/2019 Bitemporal Heteronymus Hemianopia

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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.

Bitemporal Heteronymus Hemianopia

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