What is hemianopsia
Hemianopsia is a visual defect characterized by the loss of half of the visual field.
Vision of Paris: normal (A) and with hemianopsia (B left homonymous; C heteronimal binasal; D eteronima bitemporale).
E: Upper right quadrantopsia.
From: //it.wikipedia.org/wiki/Emianopsia
At the origin of this disorder there are lesions of the optical pathways which, based on their location and extension, interfere with normal visual perception.
Hemianopsia can be caused by pathological conditions of different types and degrees, including aneurysms and brain tumors.
Causes
In most cases, hemianopsia results from damage or compression at the level of the optic pathways, that is, a set of structures that, starting from the retina, connect the eyeball to the brain. This portion of the nervous system is indispensable for correct vision.
For this reason, a lesion at any level of the visual pathways compromises the normal transmission of bioelectric signals from the optic nerve to the visual cerebral cortex.
Where can the lesions that cause hemianopsia occur?
The pathological processes that cause hemianopsia can occur anteriorly, at or behind the optic chiasm. Recall that at the level of this anatomical formation, the fibers that make up the optic nerves intersect partially, before continuing in the optical traits.
Based on this criterion, the lesions that can cause hemianopsia are divided into:
- Prechiasmatics : 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;
- Backchiasmatic : affecting the posterior part of the chiasm, that is the optic tracts or the pathways placed inside the diencephalon.
Symptoms
Hemianopsia is an alteration of vision characterized by the abolition of a half of the visual field.
In particular, the disturbance 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 hemianopsia ).
Furthermore, they are distinguished:
- Bitemporal heterogeneous hemianopsia : loss of the temporal visual field of each eye by median lesion of the optic chiasm (in practice, it is as if the patient had a blinker);
- Binasal heterogeneous hemianopsia : loss of the nasal visual field due to bilateral lesions interesting both sides of the optic chiasm (very rare);
- Homonymous hemianopsia : loss of the right or left visual field due to lesion, respectively, of the left or right optic tract;
- Quadrantopsy : loss of only one quadrant of the visual field.
Associated diseases
Hemianopsia is often due to compression of the optic pathways exerted by brain tumors and aneurysms that progressively increase in size.
This disorder can also occur in the event of:
- Carotid aneurysm;
- Stroke;
- Cerebral ischemia;
- Intracranial hemorrhages;
- Meningitis;
- Head trauma;
- Pituitary tumors.
Diagnosis
Hemianopsia must be considered a symptom and not a disease in itself. Unfortunately, some of the aforementioned pathological conditions may not give any sign; consequently the patient becomes aware of the problem only after the reduction of the visual field.
For this reason, when you suspect you have visual impairment, it is advisable to go immediately to the ophthalmologist for a thorough visit. Based on the suspected diagnosis, further investigations will be indicated to identify the exact cause of hemianopsia.
Treatment
The treatment of hemianopsia varies according to the underlying pathology.
In some cases, it is sufficient to remove the cause that caused this deficit to recover the visual capacity. 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 procedure can be used to close the damaged blood vessel.
