It is the type of partial blindness in which half of the vision of both external sides of the eye is lost.
The visual information obtained from the temporal side falls on the medial (nasal) retina. The information of the optic nerve is transferred to the optic chiasm through the nasal retina.
Bitemporal hemianopia is also known as bitemporal heteronymous hemianopia or bitemporal hemianopia. Bi means “left and right side”, temporal means “temporary visual field”, hemi means “half of each visual field” and anopia means “blindness”.
The condition manifests when there is compression in the optic chiasm. Due to compression, the impulses that are generated from the nasal retina are affected and, as a result, both temporal and peripheral vision are affected.
It basically occurs when there is compression or destruction of the optic nerve. In this condition, only the central vision remains active and this central field is sufficient to have a broad or clear vision.
In a certain way, only with the central vision the person can perform, the bitemporal hemianopia does not alter the routine activities of life.
Hemianopia is the result of a lesion of the optic chiasm. This is the area where the optic nerves on the right side of the brain cross to the left and vice versa.
The nasal retina transmits visual information of the temporal visual field and the temporal retina transmits information of the nasal field.
In the optic chiasm, the nasal fibers of the retina cross to the other side of the brain and carry information to the higher centers of the visual brain.
Therefore, a lesion in the optic chiasm affects the nasal fibers of both retinas. When this interruption in the circuit occurs, there is a loss of information from both external visual fields.
Causes of bitemporal hemianopia
The most common cause reported for bitemporal hemianopia is trauma. The trauma in the middle optic nerve. Also the compression of the optic chiasm causes the disturbance in the vision since the impulses can not be transferred due to the compression in the area.
The closest gland that is found is known as the pituitary gland, so any type of trauma to the pituitary gland such as pituitary adenomas and craniopharyngiomas can also be the cause of this condition.
Other causes include neoplastic trauma such as meningioma (it is the tumor in the meningeal tissue of the brain). Whenever there is compression of the chiasm, the communicating artery may show an aneurysm.
Symptoms of hemianopsia or bitemporal hemianopia
- The patient can not move well in crowded areas and may not have adequate vision.
- The patient can fall due to blows with objects that are in the areas that he / she transits.
- The patient may not be sure of his steps and may fall or stumble.
- The patient may not be able to read correctly and may be frustrated when he loses the sentence or a word and can not find it.
- The patient may have difficulty eating and drinking.
- The patient can not maintain the balance of his body when walking or running.
- Dizziness can also be a symptom.
- The patient may feel fear and stress during any activity.
- Panic attacks in crowded areas
There are some procedures used in the diagnosis of bitemporal hemianopia as the visual field test; In this test, lesions in the optic nerve chiasm are confirmed.
Any type of injury or defect in the pituitary gland is observed with neuroimaging. Magnetic resonance imaging and high-resolution computed tomography are also useful in diagnosing the cause of bitemporal hemianopia. The MRI test is more accurate than the CT.
Some laboratory tests are also performed to verify the performance of the endocrine glands. These will finally show the functioning of the pituitary gland.
There is no adequate treatment or cure for bitemporal hemianopia, but there may be a surgical removal of the tumor located in the pituitary gland.
Some techniques that can help:
- The technique of audiovisual stimulation helps to stimulate the patient’s vision.
- Visual restoration therapy is also effective.
- Sacral exploration training in which the patient is encouraged to look around and verify the area of visual absence.
- The optical section expanders improve the patient’s vision.
- Associated problems are also treated as difficulty in speech, paralysis, partial loss of memory and emotional disturbances may occur.