What is Hemianopia?

By May 6, 2016Blog, Hemianopia

Hemianopia, also called hemianopsia (we’ll use hemianopia here), is a type of vision loss that can happen after a stroke or brain injury which affects both eyes in the left or right side of the visual field. The amount of vision loss can be extensive or partial depending on where in the brain the injury occurred and the size of the area affected. There are several types of hemianopia. Let’s look at the most common types first.

Homonymous hemianopia

This is the most common pattern of vision loss. It affects all or most of either the right or left side of the visual field, similar to the picture on the right.

Hemianopia

Quadrantanopia

Homonymous quadrantanopia is characterised by loss of vision in one-quarter of the visual field. This picture shows almost complete loss of vision in the upper left quadrant.

Quadrantanopia

Why does vision loss often only occur on one side of the visual field?

Partial vision loss, such as hemianopia, often affects only one side of the visual field. Although it might feel that vision has been affected in one eye only, more often the damage occurred in the visual pathways that carry information from one side of both eyes to the brain. For instance, if the left side of the visual field has been affected, the visual pathways carrying information from both eyes to the right side of the brain have been damaged. And vice versa—when vision on the right hand side has been affected, it means that the damage has occurred in the pathways carrying visual information to the left side of the brain.

Less common types of visual loss

Altitudinal hemianopia affects the upper (superior) or lower (inferior) half of the visual field on both sides. It can be caused by damage to the optic nerve such as in ischemic optic neuropathy, which is when the blood supply to the optic nerve is inadequate. The pictures below show how the visual field can be affected in superior (left) and inferior (right) altitudinal hemianopia.

superioraltitudinalhemianopia

inferioraltitudinalhemianopia

In bitemporal hemianopia, vision loss occurs in both outer halves of the visual field, like in the picture below. It’s usually caused by damage to the optic chiasm, where the nerves from both eyes cross over.

bitemporalhemianopia

Binasal hemianopia affects the inner halves of the visual field (close to the nose) in both eyes. It can also be caused by ischemic optic neuropathy (poor blood supply to the optic nerve), but sometimes by other types of damage in the brain or within the eyes.

binasalhemianopia

How does hemianopia affect daily life?

Although hemianopia can improve in the days and months after a stroke, around 20–28% 1 of people will be left with some degree of vision loss. The impact on daily life can be huge in some cases—it’s easy to understand why from the pictures above. And it’s not unusual for people become afraid of going out on their own because of the risk of falling, bumping into other people, not being able to cross roads safely, or not being able to find their way around, especially in unfamiliar places. It’s important to have the type of vision loss properly diagnosed so that appropriate help can be given, such as optical aids and visual scanning training. Compensatory therapies such as NeuroEyeCoach can help train people to scan their visual field more effectively, to bring previously unnoticed objects into view and make the most of the remaining vision. Restorative therapies such as Neuro-Eye Therapy and VRT are the only therapies that can actually help to reduce the area of vision loss and improve visual sensitivity in the damaged area.

Other visual problems can happen after a stroke

Hemianopia is not the only type of vision problem that can occur after a stroke. A future blog post will look into other types and how they can be helped.

References

  1. M Ali, C Hazleton, P Lyden, A Pollock, M Brady. Recovery from Poststroke Visual Impairment: Evidence From a Clinical Trials Resource. Neurorehabil Neuro Repair. 2013; 27(2): 133–141.

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