Bitemporal Heteronymus Hemianopia

Roll No. 222 Muhammad Mubashir Tanvir

Roll No. 223 Muhammad Adnan Haider

Clinical scenario:

• A 61-year-old male had problems with his vision while driving and was bothered by the light. He couldn't see the vehicles on his right and left sides. These complaints started gradually several months ago. He saw a local eye doctor who found abnormal visual fields and referred him to endocrinology. An MRI was done.�What is the diagnosis?

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.

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• Hemi-anopia means the absence of vision in half of the visual field of one eye.

Pathophysiology

• VISUAL PATHWAYS:

A normal visual pathway has the following components:

• Retina
• Optic nerves
• Optic chiasm: where optic nerve fibres from the nasal hemiretina of both sides decussate and pass to the opposite optic tract.
• Optic tracts
• LGN
• Optic Radiation or geniculocalcarine tract
• Primary Visual Cortex or Brodmann’s Area 17

In bitemporal hemianopia, the lesion or damage occurs in the region of OPTIC CHIASM.

*(labelled B)*

• VISUAL FIELDS:

“The field of vision is the visual area seen by an eye at 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 the temporal 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 the image of the field of vision is inverted on the retina by the OPTICAL SYSTEM of the eye.

Paris as seen with normal eyes.

Paris as seen with bitemporal heteronymus hemianopia.

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 heteronymus although both sided temporal visual fields are involved?

The word heteronymus/homonymus hemianopia is used for the LEFT OR RIGHT sides of visual fields of both 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

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• Aneurysm in the anterior communicating artery which passes superior to the chiasm.

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Pituitary tumor causing lesion.

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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Computerized and antique perimeters

• CONFRONTATION TESTING:
• It is the bedside method of determining the visual fields.
• The doctor and patient are focussed on each other and eye to eye.
• The doctor makes sure whether the finger in his visual field is also in the patient’s field of vision or not.
• Flicks his fingers or shows a number to count.

• RELATION WITH PITUITARY TUMOR:

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When there is pituitary tumor as the underlying cause, as it is most common, the levels of various hormones in the body are upset.

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Eg, TSH, T3, T4, Prolactin, etc.

Therefore, blood levels of these hormones are also determined.

Cure and Treatment

• There is usually no cure for hemianopias, but in some cases surgical procedure for removing pituitary 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 combination of these treatments.

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