Hemianopia is a reduction or loss of vision in one half of the visual field. Depending on the case, it can be considered unilateral or bilateral, lateral or altitudinal, homonymous or heteronymous. This vision disorder is caused by nerve damage to the optic nerve.

Hemianopia is a visual disorder that affects a visual hemfield, that is to say only one half of the visual field of the eye. It can be unilateral, affecting the sight of one eye, or bilateral, affecting the visual acuity of both eyes.

In some cases, hemianopsia can be distinguished from quadranopsia. The latter only concerns part of the visual hemisphere. Depending on its location, the quadranopsy can be said to be left or right, lower or upper.

How is hemianopsia manifested?

Hemianopia is caused by nerve damage to the optic nerve, the sensory cranial nerve connecting each eyeball to the brain. Depending on the area of ​​the affected nerve, this visual disturbance can manifest itself differently in the eye. The visual field of the eye can be divided according to:

• a vertical axis, with a lower visual hemisphere and an upper hemisphere;
• a horizontal axis, with a left visual hemfield and a right visual hemfield, or with an exterior visual hemfield (temporal visual hemfield located near the temples) or interior (nasal visual hemisphere).

What are the different types?

Depending on the case, it is possible to distinguish several types of hemianopsies:

• homonymous lateral hemianopia, the most frequent, when the same visual hemisphere, either left or right, is affected at the level of both eyes;
• heteronymous lateral hemianopia, more often called heteronymous hemianopia, when the vision of both eyes is impaired either in the temporal visual hemianopia (bilateral hemianopia) or in the nasal visual hemianopia (binasal hemianopia);
• altitudinale hémianopsie, a rare form, when the lower or upper visual hemfield is affected.

The nerve damage responsible for hemianopsia can have several causes. These are generally of tumor, vascular or traumatic origin.

Causes of tumor origin

The development of a tumor in the brain can compress the optic nerves and cause homonymous or heteronymous lateral hemianopia. Visual loss can, for example, be due to the development:

• a pituitary adenoma, a benign, non-cancerous tumor of the pituitary gland, an endocrine gland in the brain;
• an meningioma, a generally benign tumor that develops in the meninges, membranes covering the brain and spinal cord;
• of a gliome, a benign or malignant tumor that appears in the glial tissue, the tissue supporting neurons.

Causes of vascular origin

The homonymous lateral hemianopia can also be the consequence of stroke (Stroke), or stroke. A stroke is caused by a blood flow disorder in the brain.

Causes of traumatic origin

In some cases, the nerve damage causing hemianopia is due to head trauma.

The consequences and the course of hemianopsia depend on many parameters including the origin of the nerve damage. In the most serious cases, the visual disturbance may worsen and become irreversible. Early medical treatment is necessary to limit the risk of complications.

The medical management of hemianopsia is generally based on the treatment of the nerve damage. Depending on its origin, it may sometimes require surgery.

The treatment of hemianopsia is generally accompanied by optical rehabilitation sessions. Carried out by an orthoptist, this rehabilitation allows the patient to adapt to his visual field.