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Synonyms and keywords: Bitemporal hemianopsia
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 a patient because one tends to focus conscious attention more on objects in the center 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. "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 and anopsia: blindness (formed by a(n) no + opsis vision + ia).
- First case of Bitemporal hemianopsia was first reported by Clarence A. Veasey, in 1904 .
Bitemporal hemianopia may be classified according to the number of defective optic fibers into Complete bitemporal hemianopia and Partial bitemporal hemianopia.
- Bitemporal hemianopia is a visual defect due to a lesion involving optic chiasm.
- While afferent sensory inputs from superior temporal quadrant of visual field are relayed through inferior nasal fibers of optic nerve, the inputs from inferior temporal quadrant are relayed through superior nasal fibers. Similarly the visual information from superior nasal quadrant and inferior nasal quadrant are relayed through inferior temporal fibers and superior temporal fibers respectively .
- Optic chiasm is an anatomical structure in middle cranial fossa formed by decussation of nasal fibers of optic nerve travelling from retina to visual cortex.
- A lesion involving optic chiasm either due to compression (eventually leading to vascular compromise) or vascular compromise, disrupts nasal fibers of optic nerve almost always resulting in bilateral defects in temporal half of visual field.
- A lesion compressing the chiasm from below (eg: Pitutary tumors) will have predominant defects in superior temporal quadrants along with partial defects in inferior temporal quadrant and Vice-versa.
Most of the causes of bitemporal hemianopia are due to disorders of the pituitary gland and its surrounding structures.
Causes by Organ System
|Cardiovascular||No underlying causes|
|Chemical / poisoning||No underlying causes|
|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, Obstructive hydrocephalus, Traumatic chiasmal syndrome, Dolichoectasia of internal carotid arteries|
|Nutritional / Metabolic||No underlying causes|
|Obstetric/Gynecologic||Hypophyseal hypertrophy in pregnancy|
|Oncologic||Adamantinoma of sella turcica, Craniopharyngioma, Glioma of third ventricle, Pituitary macroadenoma, Prolactinoma, Meningioma, Suprasellar tumors|
|Opthalmologic||Dermatochalasis, Optic neuropathy, Optic chiasmal syndrome, Bilateral blepharoptosis, Traumatic chiasmal syndrome|
|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||Traumatic chiasmal syndrome|
|Urologic||No underlying causes|
|Dental||No underlying causes|
|Miscellaneous||No underlying causes|
Causes in Alphabetical Order
- Adamantinoma of sella turcica
- Aneurysm of anterior communicating artery
- Bilateral blepharoptosis
- Chloroquine retinopathy
- Chronic chiasmal arachnoiditis
- Dolichoectasia of internal carotid arteries
- Enlarged third ventricle
- Glioma of third ventricle
- Hypophyseal hypertrophy in pregnancy
- Intracranial vascular loop
- Obstructive hydrocephalus
- Optic chiasmal syndrome
- Optic neuropathy
- Pituitary macroadenoma
- Suprasellar tumors
- Traumatic chiasmal syndrome
- Veasey CA (1904). "Observations of a case of bi-temporal hemianopsia with some unusual changes in the visual fields". Trans Am Ophthalmol Soc. 10 (Pt 2): 383–7. PMC 1322445. PMID 16692037.
- Hoyt WF (1970). "Correlative functional anatomy of the optic chiasm. 1969". Clin Neurosurg. 17: 189–208. doi:10.1093/neurosurgery/17.cn_suppl_1.189. PMID 4939481.