Bitemporal hemianopsia (or Bitemporal hemianopia) is the medical description of a type of partial blindness

Blindness

Blindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...

 where vision is missing in the outer half of both the right and left visual field. It is usually associated with lesions of the optic chiasm

Optic chiasm

The optic chiasm or optic chiasma is the part of the brain where the optic nerves partially cross...

, the area where the optic nerves from the right and left eyes cross near the pituitary gland.

Causes

In bitemporal hemianopsia vision is missing in the outer (temporal or lateral) half of both the right and left visual fields. Information from the temporal visual field falls on the nasal (medial) retina. The nasal retina is responsible for carrying the information along the optic nerve

Optic nerve

The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...

, and crosses to the other side at the optic chiasm

Optic chiasm

The optic chiasm or optic chiasma is the part of the brain where the optic nerves partially cross...

. When there is compression at optic chiasm

Optic chiasm

The optic chiasm or optic chiasma is the part of the brain where the optic nerves partially cross...

 the visual impulse from both nasal retina are affected, leading to inability to view the temporal, or peripheral, vision. This phenomenon is known as bitemporal hemianopsia. Knowing the neurocircuitry of visual signal flow through the optic tract

Optic tract

The optic tract is a part of the visual system in the brain.It is a continuation of the optic nerve and runs from the optic chiasm to the lateral geniculate nucleus....

 is very important in understanding bitemporal hemianopsia.

Bitemporal hemianopsia most commonly occurs as a result of tumors located at the mid-optic chiasm. Since the adjacent structure is the pituitary gland, some common tumors causing compression are pituitary adenoma

Pituitary adenoma

Pituitary adenomas are tumors that occur in the pituitary gland, and account for about 15% of intracranial neoplasms. Tumors which exceed 10 mm in size are defined as macroadenomas, and those smaller than 10 mm are referred to as microadenomas...

s, and craniopharyngioma

Craniopharyngioma

Craniopharyngioma is a type of brain tumor derived from pituitary gland embryonic tissue, that occurs most commonly in children but also in men and women in their 50s and 60s....

s. Also another relatively common neoplastic etiology is meningioma

Meningioma

The word meningioma was first used by Harvey Cushing in 1922 to describe a tumor originating from the meninges, the membranous layers surrounding the CNS ....

s. An etiology of vascular origin is an aneurysm

Aneurysm

An aneurysm or aneurism is a localized, blood-filled balloon-like bulge in the wall of a blood vessel. Aneurysms can commonly occur in arteries at the base of the brain and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart...

 of the anterior communicating artery

Anterior communicating artery

In human anatomy, the anterior communicating artery is a blood vessel of the brain that connects the left and right anterior cerebral arteries....

 which arise superior to the chiasm, enlarge, and compress it from above.

Etymology

The absence of vision

Visual perception

Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...

 in half of a visual field

Visual field

The term visual field is sometimes used as a synonym to field of view, though they do not designate the same thing. The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments", while 'field of view' "refers to the physical...

 is described as hemianopsia

Hemianopsia

Hemianopia, or hemianopsia, is a type of anopsia where the decreased vision or blindness takes place in half the visual field of one or both eyes. In most cases, the visual field loss respects the vertical midline...

.

The visual field of each eye can be divided in two vertically, with the outer half being described as temporal, and the inner half being described as nasal.

"Bitemporal hemianopsia" can be broken down as follows:

• 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 a(n) ^no + opsis ^vision + ia)

External links

• Case report of Bilateral Hemianopsia Due to Pituitary Adenoma. Clinical Cases and Images. at blogspot.com