What is hemianopsia
Hemianopia is a vision defect characterized by the loss of half of the visual field.
Paris view: normal (A) and with hemianopia (B left homonymous; C binasal heteronym; D heteronym bitemporal).
E: Right superior quadrantopsia.
From: https://it.wikipedia.org/wiki/Emianopsia
At the origin of this disorder there are lesions of the optic pathways which, according to their location and extent, interfere with normal visual perception.
Hemianopia can be caused by various types and degrees of pathological conditions, including aneurysms and brain tumors.
Causes
In most cases, hemianopia derives from damage or compression at the level of the optical pathways, that is, the set of structures that, starting from the retina, connect the eyeball to the brain. This portion of the nervous system is essential for correct vision.
For this reason, a lesion at any level of the optical pathways impairs the normal transmission of bioelectrical signals from the optic nerve to the visual cerebral cortex.
Where can the lesions that cause hemianopia occur?
Pathological processes that cause hemianopia can occur anterior to, at, or posterior to the optic chiasm. Recall that at the level of this anatomical formation, the fibers that make up the optic nerves partially cross, before continuing in the optic tracts.
According to this criterion, the lesions that can cause hemianopia are divided into:
- Prechiasmatiche: the pathological conditions affect the segments preceding the chiasm; the interruption of conduction at the level of the optic nerve leads to the exclusion of the visual field of the corresponding side (right or left);
- Chiasmatics - pathological processes occur at the same level as the optic chiasm;
- Retrochiasmatic: they affect the posterior part of the chiasm, ie the optic tracts or the pathways located inside the diencephalon.
Symptoms
Hemianopia is an alteration of vision characterized by the abolition of one half of the visual field.
In particular, the disorder may concern:
- Half of the right or left visual field (lateral or vertical hemianopia);
- Half of the upper or lower visual field (altitudinal or horizontal hemianopia).
In addition, the following are distinguished:
- Bitemporal heteronomous hemianopia: loss of the temporal visual field of each eye due to a median lesion of the optic chiasm (in practice, it is as if the patient had a blinker);
- Binasal heteronomous hemianopia: loss of the nasal visual field due to bilateral lesions affecting both edges of the optic chiasm (very rare);
- Homonymous hemianopia: loss of the right or left visual field due to lesion, respectively, of the left or right optic tract;
- Quadrantopsia: loss of only one quadrant of the visual field.
Associated diseases
Often, hemianopia is due to compression of the optic pathways exerted by brain tumors and aneurysms that progressively increase in size.
This disorder can also occur in case of:
- Carotid aneurysm;
- Stroke;
- Cerebral ischemia;
- Intracranial hemorrhages;
- Meningitis;
- Head trauma;
- Tumors of the pituitary gland.
Diagnosis
"Hemianopia should" be considered a symptom and not a disease in its own right. Unfortunately, some of the aforementioned pathological conditions may not show any signs; consequently the patient only realizes the problem after the visual field has been reduced.
For this reason, when there is a suspicion of having visual deficits, it is advisable to immediately go to the "ophthalmologist for a" thorough examination. Based on the diagnostic suspicion, further investigations aimed at identifying the exact cause of the hemianopia will be indicated.
Treatment
Treatment of hemianopia varies according to the underlying disease.
In some cases, it is sufficient to remove the cause that led to this deficit to regain vision. When a pituitary tumor is present, for example, a "surgical removal of the neoplastic mass can be performed, while in the case of an aneurysm, an embolization operation can be used to close the damaged blood vessel."
