science

Hemianopsia

Hemianopsia is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Hemianopsia rather than just read about it. In short: Hemianopsia, or hemianopia, is a loss of vision or blindness (anopsia) in half the visual field, usually on one side of the vertical midline. The most common causes of this damage are stroke, brain tumor, and trauma.

Key takeaways

Hemianopsia belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Hemianopsia to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hemianopsia from memory before moving on to harder problems.

Reference excerpt

Hemianopsia, or hemianopia, is a loss of vision or blindness (anopsia) in half the visual field, usually on one side of the vertical midline. The most common causes of this damage are stroke, brain tumor, and trauma. This article deals only with permanent hemianopsia, and not with transitory or temporary hemianopsia, as identified by William Wollaston PRS in 1824. Temporary hemianopsia can occur in the aura phase of migraine.

Etymology The word hemianopsia is from Greek origins, where:

hemi means "half", an means "without", and opsia means "seeing".

Types When the pathology involves both eyes, it is either homonymous or heteronymous.

Homonymous hemianopsia

A homonymous hemianopsia is the loss of half of the visual field on the same side in both eyes. The visual images that we see to the right side travel from both eyes to the left side of the brain, while the visual images we see to the left side in each eye travel to the right side of the brain. Therefore, damage to the right side of the posterior portion of the brain or right optic tract can cause a loss of the left field of view in both eyes. Likewise, damage to the left posterior brain or left optic radiation can cause a loss of the right field of vision.

Heteronymous hemianopsia

A heteronymous hemianopsia is the loss of half of the visual field on different sides in both eyes. It is separated into two categories:

Binasal hemianopsia – the loss of the fields surrounding the nose; Bitemporal hemianopsia – the loss of the fields closest to the temples.

Other forms Superior hemianopsia – the upper half of the field of vision is affected, possibly because of a tumor beginning to compress the lower part of the chiasma, typically one from the hypophysis. Inferior hemianopsia – the lower half of the field of vision is affected, possibly because of a tumor beginning to compress the upper part of the chiasma, typically a craniopharyngioma.

Quadrantanopia

Quadrantanopia (quadrantanopsia or quadrantic hemianopsia) is decreased vision or blindness in one quarter of the visual field. The particular quarter of vision missing depends on whether the location of the brain damage is temporal or parietal, and the side of the lesion. For example, a lesion to the right temporal lobe with damage specifically to Meyer's loop will give rise to a left upper (superior) quadrantanopsia, while a lesion to the right parietal radiation with damage specifically to Baum's loop will result in a left lower (inferior) quadrantanopsia.

Visual neglect Visual neglect (also called hemispatial neglect or unilateral spatial neglect) differs from hemianopsia in that it is an attentional deficit rather than a visual one. Unlike patients with hemianopsia who actually don't see, those with visual neglect have no trouble seeing but are impaired in attending to and processing the visual information they receive. Whereas hemianopsia can be assuaged by allowing patients to move their eyes around a visual scene (ensuring that the entire scene makes it into their intact visual field), neglect cannot. Neglect can also apply to auditory or tactile stimuli and can even leave a patient unaware of one side of his or her own body. Ellis and Young (1998) showed that neglect can also affect patients' mental maps such that if they are asked to picture themselves standing in a familiar location and name the buildings around them, they will neglect to name the buildings on their impaired side but will be able to name them when asked to mentally face the opposite direction. Some patients with neglect also have hemianopsia, however the two often occur independent of one another.

Management Some forms of hemianopia can be treated through repeated presentations of multisensory stimuli due to the process of multisensory integration occurring in the superior colliculus. Surgical interventions have also been shown to ameliorate certain forms of hemianopia due to counterbalancing brain lesions due to a process known as the Sprague effect.

Notes

References O'Neill, E., O'Connor, J., Brady, J., Reid, I., and Logan, P. Prism Therapy and Visual Rehabilitation in Homonymous Visual Field Loss. 2011 Optometry and Vision Science, Vol. 88, No 2 February 2011. Giorgi, RG., Woods, RI., Peli, E. Clinical and Laboratory Evaluation of Peripheral Prism Glasses for hemianopsia. Optometry and Vision Science 2009; 86: 492–502.

External links

Illustrations

Worked examples

Example 1 — a first encounter with Hemianopsia

Start with the simplest possible case. Write down what Hemianopsia claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hemianopsia before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hemianopsia ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hemianopsia

In research: Hemianopsia appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Hemianopsia in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Hemianopsia is common in secondary-school and first-year university syllabi. It links to neighbouring topics Blindness, Brain disorders, Visual perception, so understanding it makes those chapters shorter.
In everyday life: Look for Hemianopsia outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Hemianopsia in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hemianopsia means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Hemianopsia out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hemianopsia in simple terms?

Why does Hemianopsia matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hemianopsia?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hemianopsia.