Bitemporal hemianopsia (or Bitemporal hemianopia) is the medical description of a type of partial 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, the area where the optic nerves from the right and left eyes cross near the pituitary gland.
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
, and crosses to the other side at the optic chiasm
. When there is compression at optic chiasm
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 hemianopia
. Knowing the neurocircuitry of visual signal flow through the optic tract
is very important in understanding bitemporal hemianopia.
Bitemporal hemianopia 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 adenomas, and Craniopharyngiomas.
The absence of vision
in half of a visual field
is described as hemianopsia
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)