Everything you ned to know about reading with hemianopia

Hemianopia, also known as hemianopsia, is a commonly misunderstood neuro-ophthalmology condition that often manifests first as a reading disorder. Patients may initially think they have a developmental disorder or an eye condition that results in partial blindness. Hemianopic patients often struggle with daily activities due to blind spots in their visual field and may have extremely limited reading skills as a result.

Here’s what to know about hemianopia, how the condition is treated, and what resources patients can use to improve reading performance and other visual deficits.

What is hemianopia?

Hemianopia is a neurology-based visual impairment condition that results in a macular sparing scotoma (a blind spot) in one-half of a person’s visual field—resulting in low vision, impaired eye movements, reading impairment, and other difficulties with visual information processing.

Types of hemianopia

There are a few different types of hemianopia, including:

• Homonymous hemianopsia — This is the most common presentation of hemianopia, where the blind field is in the same part of each eye.
  • There are three types of homonymous visual field defects:
    • Right hemianopia — Blindness occurs in the right side of each eye
    • Left hemianopia — Blindness occurs in the left side of each eye
    • Superior hemianopia — Blindness occurs in the top half of each eye
    • Inferior hemianopia — Blindness occurs in the bottom half of each eye
• Heteronymous hemianopia — This is a less common form of hemianopia that is caused specifically by lesions on the optic chasm, which results in visual field loss.
  • There are two types of heteronymous hemianopia:
    • Bitemporal hemianopia — Blindness occurs on the outer half of each eye (near the temples)
    • Binasal hemianopia — Blindness occurs on the inner half of each eye (near the nose)

Symptoms of hemianopia

Hemianopia can vary in intensity and presentation from patient to patient, but the most common symptoms of the condition are as follows:

• Loss of coordination on the affected side
• Visual disturbances like double vision, dim vision, or impaired night vision
• Not noticing objects on the affected side
• Reading problems, including reduced reading speed
• Hemifield slide phenomenon (visual fields from each eye cannot easily be integrated with one another to create a clear picture, resulting in double vision)
• Visual search disorders and other perceptual problems
• Pure alexia (selective reading impairment caused by brain damage that occurs without other language deficits)

Causes of hemianopia

Although this condition presents with visual field loss, it is not an eye condition. It occurs when the part of the brain that is responsible for interpreting images, called the visual cortex, becomes damaged or impaired in some way. The visual cortex resides in the occipital lobe of the brain in the primary cortical region and aids in the conscious processing of visually obtained data. The brain may also be injured in the area of the parietal lobe, which can also cause hemianopia.

There are multiple causes of hemianopia, including but not limited to:

• Traumatic brain injuries (TBI) sustained in car accidents, falls, and other types of blunt force trauma to the head
• Brain tumors
• Epilepsy
• Alzheimer’s disease and dementia
• Hydrocephalus
• Brain aneurysms
• Shaken baby syndrome
• Multiple Sclerosis (MS)
• Lymphoma

Diagnosing hemianopic patients

There are many ways to assess a person’s visual field and determine if there are any missing areas of vision. Diagnostic tools used to identify hemianopic patients include:

• Visual acuity assessment.
• Visual field testing.
• Reading performance assessment.

Individuals found to have visual field impairments that do not originate from the eyes themselves (such as with conditions like glaucoma) should be evaluated by a neurologist to determine if there are any correlations to brain injuries. If a patient’s eyes are healthy, but they are missing a portion of their visual field, a neurological root cause is more likely.

Treatments for hemianopia

There are several available treatments for hemianopia depending on which type the patient has and how severe the condition is. For example, patients can:

• Wear special glasses with prisms that help fill in visual field loss
• Learn to turn their head or body when looking at objects on the affected side
• Use a ruler or straight edge to follow a line of text without accidentally jumping down to the next line
• Engage in neuro-ophthalmology exercises that strengthen the brain-eye connection
• Use a guide dog to prevent injuries and falls, especially when walking or running

How can text-to-speech apps help hemianopic patients?

Patients with hemianopia often need to find reading workarounds that help them better interpret text accurately and read at a reasonable speed. Text-to-speech apps like Speechify, Natural Reader, and Voice Aloud Reader—just to name a few—can be a great way for patients with visual impairments like hemianopsia to read more quick and efficient. TTS applications and browser extensions can read multiple file types, allowing individuals the freedom to consume different types of content despite their disabilities.

Robert Slack, a Speechify customer, says of the program,

“I have hemianopia which makes it difficult to read text. This application goes above and beyond what I expect. It reads just about everything I can throw at it. It helps me reread cover letters as well as read the news. The voices speak extremely well. I think the app is a bit expensive and it needs some help getting rid of the unnecessary HTML but it works.”

People also ask

Why do persons with hemianopsia often experience difficulty reading?

In addition to the visual impairment caused by hemianopia, the areas of the brain responsible for processing reading text are usually damaged, resulting in hemianopic dyslexia and/or hemianopic alexia. The defect or blind spot in their visual field prevents patients with this condition from planning and executing proper reading saccades.

A 1995 study by J. Zihl assessed visual scanning behavior in hemianopic patients and reported that due to the loss of vision on one side of the eye, individuals have difficulty seeing upcoming words in their parafoveal vision, which reduces optokinetic movement and makes reading very difficult. A text-to-speech reader like Speechify can help people read books by listening to them with a natural-sounding voices and by following along with the highlighter if they also perfer.

What does a person with hemianopia see?

Someone with hemianopia often has double vision and cannot see at all out of the affected side of the eye. The blind spot may appear dark, white, or hazy looking, with blurred edges and a denser central point.

Does hemianopia get better?

Often, when tumors, a stroke, or another type of brain injury results in visual field loss, what has already been damaged cannot be repaired and vision cannot be recovered or restored. However, treatment interventions can usually prevent new damage and the new loss of vision. Preventative treatment can also help patients adapt to having low vision. Randomized controlled trials of treatment of hemianopsia after stroke with visual search training compared to Fresnel prisms actually excluded roughly half of potential participants because their visual impairment partially or fully resolved on its own.

What is the difference between hemianopia and hemianopsia?

The terms hemianopia and hemianopsia are generally interchangeable and refer to a kind of vision loss that occurs after certain types of brain injuries. Patients and medical professionals may use either term when referring to this condition.

What is the difference between central and peripheral vision?

Your central vision is what you are able to see directly in front of you. If you move your eyes or turn your body, whatever you are looking at straight ahead of you is in your central vision. Your peripheral vision is what you can see just outside of your central vision in the corners of your eyes.

What is the difference in reading with hemianopia and reading with a visual field defect?

Hemianopia is a type of visual field defect that causes peripheral blind spots (scotomas) that make it difficult to read the next word or next line in a text.

Why is reading with hemianopia difficult?

Conditions that impact reading ability like homonymous hemianopia tend to reduce overall reading speed and make it more difficult to comprehend written text. Individuals with hemianopia struggle with things like word length, sentence structure, returning to words they have already read, and other reading deficits.

How do you read with hemianopia?

Patients with hemianopia can read, but they tend to be much slower at it than individuals without this type of reading problem. The average person reads approximately 200 to 250 wpm. Someone with left homonymous hemianopia reads on average 137 wpm, and patients with right homonymous hemianopia tend to read at an average speed of 77 wpm.

What is the treatment for hemianopia?

Interventions for hemianopia are often focused on the rehabilitation of eye movement with compensatory therapy, as Susanne Schuett, a professor at the University of Vienna, Department of Applied Psychology, suggested in a 2009 paper on the subject. The Trauzettel-Klosinski Lab, Institute for Ophthalmic Research is a leader in the treatment of homonymous visual field defects and other low vision problems, and also recommends compensatory therapies versus restorative therapies.

A paper published in the Journal of Neurology, Neurosurgery, and Psychiatry in 2004 by authors A. Pambakian, S. Mannan, T. Hodgson, and C. Kennard discusses using saccadic visual search training as a treatment for hemianopia. This therapy trains patients to increase the efficiency of their eye movements, which allows their brain to capture what would otherwise be a missing visual field.