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This page will provide you with a comprehensive overview on the causes of hemianopia, the types of hemianopia, the symptoms of hemianopia and the treatment of hemianopia as it pertains to stroke. We sincerely hope that our website helps to further your understanding on the topic of both hemianopia and stroke. If you have further questions, please contact a healthcare professional.

What is Hemianopia?

Hemianopia, blindness in half the field of vision, is a frequent condition that occurs as a result of stroke and traumatic brain injury. The term “hemi” means half, “an” means without, and “opsia” means “seeing.” The reason hemianopia and stroke are strongly associated with each other is due to the way vision is represented in the brain.

More specifically, the visual images seen in the left side of each eye go through the right side of the brain, while the visual images we see in the right side of each eye travel through the left side of the brain. This is important when considering hemianopia and stroke because damage to the right side of the posterior brain may lead to problems in the left field of each eye and damage to the left side of the posterior brain may lead to problems in the right field of each eye.

Notably, hemianopia is different from visual neglect, a perceptual deficit, because patients with visual neglect do not have trouble seeing but rather problems with comprehending what they are seeing. In other words, patients with visual neglect have trouble processing information they receive whereas patients with hemianopia actually cannot see.

The Connection Between Hemianopia and Stroke

Hemianopia and stroke are connected by lesions in the retrochiasmal visual pathways; stroke, insufficient blood flow to the brain, may cause these lesions non-specifically. The retrochiasmal pathways, parallel streams of information sent to the brain for identification, storage and retrieval, are essential for an individual’s sense of sight. Specifically, the part of retrochiasmal pathways that are important include: the optical tract, the optical radiations and the occipital cortex. Each of these areas are relevant in diagnosing hemianopia because the location of the lesion helps determine the visual field abnormality, the symptoms and the characteristics, such as the size, form, and type.

How Vision Works

Before we can understand how hemianopia and stroke are connected, it is essential to understand the structure and the basic process of visual perception. Visual perception, the ability to interpret information in the environment through sight, is a complex process that involves both the eyes and the brain. When a person senses light stimuli with their eyes, various rods and cones within the eye are activated through a series of chemical reactions. This information is then relayed to the brain through the optic nerve and processed in the occipital lobe.

The brain’s specific job is to interpret, categorize and characterize the information it receives. Importantly, the retinal and optic nerve fibers are on both the right and left side of the eye. The information from the right side of the eye represents the left side of the visual field whereas the information from the left side of the eye represents the right side of the visual field. This is simply because the optic nerve that exits each eyeball crosses over to the opposite side on its way to the brain.

However, it is important to note that only the nasal fibers (closest to the nose) crossover, not the temporal fibers (part of the eye closes to the temple). Consequently, in the right eye the right part of the visual field crosses over to the left side of the brain but the left part of the visual field does not. Likewise, information from the left side of the visual field in the left eye crosses to the right side of the brain but the right part of the visual field does not. The point where the fibers cross are called the optic chiasm. If the damage is before or at the optic chiasm, the patient’s right eye would have a loss of the right visual field and the patient’s left eye would have a loss of the left visual field.

In contrast, if the injury is after the fiber crosses, a loss of the left visual field of each eye would be due to damage to the right side of the brain and a loss of the right visual field would be due to damage to the left side of the brain. Simply put, the location of the damage in hemianopia and stroke would determine how the patient is affected.

Types of Hemianopia

There are many different types of hemianopia that may exist in an individual that has hemianopia and stroke. This is simply because the lesions hemianopia and stroke are not restricted to only certain locations. Importantly, any intracranial lesion in the various components of the retrochiasmal pathway may cause one of the various types of hemianopia. The most common types of hemianopia include:

Homonymous hemianopia: This is the most common form of hemianopia and commonly occurs when the patient has both hemianopia and stroke. It is when a patient loses half of their visual field in both eyes on the same side. For example, if a patient has damage to the left side of the posterior brain, they will have a loss of vision in the right field of both eyes.

Heteronymous hemianopia: This is when a patient loses half of their vision in both eyes on opposite sides. Importantly, it can be binasal (around the nose) or bitemporal (the side closest to the temple)

Superior hemianopia: Superior hemianopia is when the patient loses the upper half of visual field in both eyes.

Inferior hemianopia: Inferior hemianopia is when the patient loses the lower half of the visual field

Quadrantanopia: If a patient loses one quarter of the visual field in both eyes, it is called quadrantanopia. Importantly, the specific quarter affected depends on the location of the brain damage.

Causes of Hemianopia

Some of the most important causes of hemianopia are stroke, brain tumour, and trauma. It is important to recognize, however, that although any type of lesion may be one of the causes of hemianopia, certain types of hemianopia are more frequently associated with certain causes. For example, the two main causes of homonymous hemianopia are cerebral infarction and intracranial hemorrhage. Although homonymous hemianopia may be also be a result of brain tumours, for the most part it occurs when the patient has hemianopia and stroke. This is an important consideration when analyzing the potential symptoms of hemianopia and the treatment of hemianopia.

Symptoms of Hemianopia

Although there are various types of hemianopia, the symptoms of hemianopia are simply decreased vision or blindness. A patient with hemianopia and stroke can typically tell something is wrong with their vision instantly because they will have either a blind spot or part of the visual field will be broken. Importantly, a person may not recognize that this blindness is in both eyes due to the way sight works; the brain may attempt to compensate any loss of vision by filling in some areas on one side.

Treatment for Hemianopia

The treatment for hemianopia typically depends on the patient’s age, type of hemianopia and how long they had the condition for. Some common methods used in the treatment for hemianopia includes:

Audiovisual Stimulation Training: This form of therapy is commonly used for homonymous hemianopia. It uses the combination of sound and light to stimulate areas associated with the visual field.

Saccadic eye movement training: This form of therapy is also used primarily to treat homonymous hemianopia. It involves teaching the patient to scan their environment by moving their eyes to fill in the missing parts of their visual field

Optical visual span expanders: This type of treatment involves glasses that have a special prism mounted on them. The prism increases the visual field, and thus, the patient can incorporate the image from the glasses to the rest of the visual field in order to produce a more complete image.

Visual Restoration Therapy: Visual restoration therapy is a prescription computer program that is tailored specifically to the individual’s needs. In this type of therapy the patient focuses on a central fixation point while light stimuli is shows up in different positions. The patient is asked to respond to the stimuli accordingly.

Importantly, there is no treatment for hemianopia that can cure hemianopia and stroke. This is simply because both are brain injuries. Consequently, the primary focus of medical professionals is to help patients have a better perception of the world around them and compensate for their condition. For this reason, doctors often recommend combining various therapies in the treatment for hemianopia.

Living with Hemianopia after Stroke

Living with hemianopia after stroke is difficult for patients because they are unable to completely perceive the environment around them. In turn, this may cause a patient to run into objects, fall or be surprised by unnoticed objects. Ultimately, this may affect a patient’s quality of life because they may become overly cautious, afraid of travelling in public places or less motivated. For this reason, it is essential for the patient to understand the implications of hemianopia and stroke, as well as seek help from a medical professional.

For any additional information on hemianopia and stroke please contact your local healthcare professional.