A blockage in the visual nervous system can cause partial blindness in one or both eyes. Nerves run from the eye to different parts of the brain, where problems with the neurotransmitters can occur in all those places. The further a blockage is located in the brain, the less the influence of blindness. In other words, the closer to the eye a blockage occurs, the more blindness will occur. What is hemianopia and how can a patient with semi-blindness be helped?

Semi-blindness, hemianopia

• Disrupted neurotransmitters
• Varying degrees of hemianopia
• Why no blindness of the inner visual field?
• What can be done about half blindness?

Disrupted neurotransmitters

The condition in which the left half or right half of the visual field is lost due to blindness is called hemianopia. Normally people are blind about:

• the left half of the left eye or;
• the right half of the right eye.

This can also occur at the same time. In that case there is bilateral hemianopia. In these cases there is nothing wrong with the eye, but there are disturbances in the neurotransmitters. Neurotransmitters ensure that information is sent from the eye retina to the brain via the visual nerve pathways. Often damage has occurred, blocking the signals.

Varying degrees of hemianopia

The nerve pathways running from the eyes to the brain cross and branch again in the left and right halves of the brain. Neurotransmitter blockages can occur in various places in the brain, causing some vision to disappear. The following blockages are possible:

• blockage to the junction by a tumor results in complete blindness of that eye, while the other eye can still see;
• blockage at the junction by a tumor results in bilateral hemianopia, in which both eyes are still half-sighted and therefore half-blind;
• blockage after the junction for the bifurcation results in blindness of the left half or right half of both eyes;
• blockage after the bifurcation results in blindness of a quarter of both eyes. This can occur both above and below on the same side.

Additional symptoms may be that the color and direction of an object can be perceived, but the object itself cannot. Then there is blindsight.

Why no blindness of the inner visual field?

Because both eyes supply part of the inner visual field, it is virtually impossible for this part to disappear. Blindness mainly affects that part of the visual field to which the other eye does not contribute. In other words, it concerns the outer left and right parts of the visual field. A symptom of hemianopsia is that objects are not easily noticed, so they are bumped into. There may also be difficulty reading and writing, and facial recognition may partly disappear.

What can be done about half blindness?

Hemianopsia can be treated in three ways. Please note that these are not intended to remove the transmitter blockage. Consider the following visual aids:

• learning to look better. Make optimal use of the remaining field of view. This is intended to allow you to view the environment more with eye and head movement, so that a more complete picture of the environment is passed on to the brain;
• one way is to enlarge the existing visual field by stimulating the affected visual field. This is accomplished through visual training. This is the so-called visual restitution therapy and is still in the development stage;
• use prism glasses. The visual image is thus shifted so that the invisible part is perceived by the still working field of view.

, the patient’s field of vision can be significantly improved, so that the person with semi-blindness can still go through life well.

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