Bitemporal hemianopia

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Aditya Govindavarjhulla, M.B.B.S. [2]

Synonyms and keywords: Bitemporal hemianopsia

Overview

Bitemporal hemianopia is a specific type of visual disturbance in which sight in the outer half of the visual field of each eye is lost. As a result, the patient retains central vision but loses sight at the edges of his or her vision. This is not always obvious to him or her, even when the damage is quite severe on objective testing, because one tends to focus attention more on objects in the centre of the visual field.

Hemianopia signifies a loss of half of the visual field, and bitemporal denotes the two lateral, or temporal, sides of the head. By contrast, homonymous hemianopia signifies that the same half of each visual field is lost, ie all vision on the left, or on the right, of the midline. Such a pattern of visual loss is caused by damage to the more distal part of the optic radiation, most commonly by a stroke.
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Etymology

"Bitemporal hemianopia" 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
• anosia: blindness (formed by a(n) ^no + opsis ^vision + ia)

Pathophysiology

Hemianopia results from lesion of optic chiasm. This is the area where optic nerves from right cross over to the left and vice versa. Visual information from the temporal visual field falls on the nasal retina and information from nasal field falls on temporal retina. At optic chiasm nasal fibers of retina cross over to other side and carries information to higher centers.

So, when there is a lesion of optic chiasm the nasal fibers of both the retina are affected leading to loss of information from both the temporal fields.

Differential Diagnosis

Common causes

• Pituitary macroadenoma
• Craniopharyngoma
• Meningioma
• Aneurysm of anterior communicating artery

Causes based on organ system

Cardiovascular	No underlying causes
Chemical / poisoning	No underlying causes
Dermatologic	Dermatochalasis
Drug Side Effect	Chloroquine retinopathy
Ear Nose Throat	No underlying causes
Endocrine	Pituatary macroadenoma, Prolactinoma
Environmental	No underlying causes
Gastroenterologic	No underlying causes
Genetic	No underlying causes
Hematologic	No underlying causes
Iatrogenic	No underlying causes
Infectious Disease	No underlying causes
Musculoskeletal / Ortho	No underlying causes
Neurologic	Chloroquine retinopathy, Pituitary macroadenoma, Prolactinoma, Craniopharyngioma, Aneurysm of anterior communicating artery, Intracranial vascular loop, Meningioma, Enlarged third ventricle, Glioma of third ventricle, Chronic chiasmal arachnoiditis, Suprasellar tumors, Adamantinoma of sella turcica, Optic neuropathy, Optic chiasmal syndrome, Traumatic chiasmal syndrome
Nutritional / Metabolic	No underlying causes
Obstetric/Gynecologic	Hypophyseal hypertrophy in pregnancy
Oncologic	No underlying causes
Opthalmologic	No underlying causes
Overdose / Toxicity	No underlying causes
Psychiatric	No underlying causes
Pulmonary	No underlying causes
Renal / Electrolyte	No underlying causes
Rheum / Immune / Allergy	No underlying causes
Sexual	No underlying causes
Trauma	No underlying causes
Urologic	No underlying causes
Dental	No underlying causes
Miscellaneous	No underlying causes