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.