Homonymous Hemianopia – Healthnile.com

Homonymous hemianopia can be unsettling because it changes how a person sees the world. This condition blocks vision on the same side of both eyes, often making daily tasks like reading, driving, or even walking more difficult. A stroke that damages the part of the brain responsible for processing vision most commonly causes homonymous hemianopia.

Other conditions can also lead to this type of vision loss. Brain injuries, tumors, inflammation, or infections may disrupt the visual pathways and trigger the problem. Even less common factors, such as seizures or migraines, can sometimes play a role.

Definition of Symptom

Homonymous hemianopia, also called homonymous hemianopsia, is a type of visual field loss. It affects the same side of the visual field in both eyes. For example, in left homonymous hemianopsia, the left half of vision is missing in each eye.

The term hemianopia (or hemianopsia) means loss of half of the visual field. This can be complete, where an entire half is gone, or partial, where only a section is missing. A related condition is quadrantanopia, which involves loss of one-quarter of the visual field. There are several types of hemianopia:

Homonymous Hemianopia: Same side of both eyes.
Heteronymous Hemianopia: Opposite sides in each eye.
Bitemporal Hemianopsia: Outer halves of both eyes are lost.
Complete Hemianopia: Full half of vision is gone.
Superior Quadrantanopia: Upper quarter of vision is missing.

These symptoms usually come from damage in the brain rather than the eyes. The visual pathways in the brain control opposite sides of vision. For example, the right side of the brain processes the left visual field of both eyes. People with hemianopia may notice missing areas when reading, walking, or recognizing objects. They may feel like one eye is weaker, but testing shows the same side is gone in both eyes.

Possible Causes/Diseases Condition

Cause Category	Examples
Vascular	Stroke, posterior cerebral artery stroke, arteriovenous malformations
Traumatic	Brain injury, traumatic brain injury
Tumors/Lesions	Brain tumors, lymphoma, brain lesion
Infections	Neurosyphilis, other brain infections
Degenerative/Other	Alzheimer’s disease, multiple sclerosis, epilepsy

A stroke, especially when it affects the posterior cerebral artery, often causes homonymous hemianopia. Both ischemic strokes (from blood clots) and hemorrhagic strokes (from bleeding) can damage the visual pathways in the brain.
Brain injuries from trauma, such as car accidents or falls, can also lead to this condition. When a traumatic brain injury disrupts the optic tract or occipital lobe, vision loss on the same side of both eyes can occur.
Brain tumors can press on or destroy parts of the visual pathway. Tumors, whether benign or malignant, as well as conditions like lymphoma or other brain lesions, can have similar effects, especially near the occipital cortex.
Some infections such as neurosyphilis can damage brain tissue and lead to visual field loss. Chronic diseases like multiple sclerosis may also cause nerve damage that interrupts visual processing.
Other neurological conditions linked to hemianopia include epilepsy, Alzheimer’s disease, and complications from neurosurgical procedures. Treatments such as chemotherapy can sometimes contribute if they affect brain tissue.
Vascular abnormalities, such as arteriovenous malformations, can result in bleeding or pressure on the visual pathways. Less commonly, eye-related conditions like glaucoma can combine with brain damage to worsen vision loss.

Other Non-Disease Causes

Not all cases of homonymous hemianopia come from disease. Some result from external factors or medical procedures that affect the brain’s visual pathways.

Head trauma frequently causes non-disease-related cases. Car accidents, falls, or sports injuries can damage areas such as the optic tract or occipital lobe, leading to partial vision loss.
Surgical interventions on the brain may also cause this condition. Operations near the occipital cortex or optic radiations sometimes disrupt normal visual processing.
Radiation therapy for brain tumors can harm surrounding tissue. Even when used to treat another problem, radiation may injure the visual pathways and create lasting field defects.

Doctors use several tools to confirm vision loss from these non-disease causes:

Visual field testing (such as automated perimetry or confrontation visual field testing).
Neuroimaging methods like MRI and CT scans (computed tomography).
Eye exams that check visual acuity and assess the retina.
Optical coherence tomography to evaluate nerve fiber layers.

A simple table shows how these methods help:

Test/Tool	Purpose
MRI / CT scan	Locate brain injury or radiation effects.
Visual field test	Map missing areas of vision.
Eye exam	Rule out eye-specific problems.
Optical coherence tomography	Check optic nerve health.

How It Causes the Symptom

Homonymous hemianopia develops when damage occurs along the visual pathways in the brain. These pathways carry information from the eyes through the optic nerve, optic chiasm, optic tract, lateral geniculate nucleus, optic radiations, and finally to the occipital lobe where the visual cortex processes sight.

When injury or stroke affects one side of these pathways, the brain cannot process the corresponding half of the visual field from both eyes. This creates a visual field defect on the same side, leading to partial vision loss. The pattern of loss depends on where the damage occurs:

Optic tract or lateral geniculate nucleus → loss of vision on one side of both eyes.
Optic radiations → incomplete or patchy visual field deficits.
Occipital lobe (often supplied by the posterior cerebral artery) → complete hemianopia, sometimes with macular sparing.

Macular sparing happens when central vision remains intact despite side field loss, because the macula has dual blood supply and may be preserved. This condition does not usually cause double vision, but it reduces visual function and creates significant visual impairment.

People may struggle with reading, walking safely, or noticing objects on the affected side. In some cases, prism glasses or prismatic correction can shift images from the missing field into the seeing field, helping patients adapt to the loss of vision. These tools do not restore sight but can improve awareness of the environment.

Possible Complications

Homonymous hemianopia can create many daily challenges. People may struggle with reading difficulties, since words on one side of the page are missing from their field of view. Mobility and safety are also affected. Patients may bump into objects, have trouble with obstacle avoidance, or feel unsafe walking in crowded areas.

Cognitive and psychological issues can appear as well. Some individuals experience visual hallucinations, dizziness, or confusion. Others may develop hemispatial neglect, where they ignore one side of space. Communication problems may occur if the brain injury also affects language areas, leading to aphasia. This can complicate daily interactions.

When to Seek Medical Attention

Homonymous hemianopia often starts suddenly, especially when stroke or head injury causes it. Anyone who notices sudden loss of vision on the same side of both eyes should treat it as urgent and contact a healthcare provider right away. Seek medical help if you experience:

Sudden vision loss on one side.
Difficulty reading or tracking text.
Bumping into objects on the affected side.
Headaches, dizziness, or nausea with vision changes.

An ophthalmologist can determine whether the vision loss comes from the eyes or the brain. In many cases, a neuro-ophthalmologist or neurologist may help identify the cause. If symptoms appear for the first time, especially after a stroke or trauma, seek emergency evaluation. For ongoing care, patients should work with their healthcare team, which may include:

Specialist	Role
Ophthalmologist	Examines eye health and rules out eye disease.
Neuro-Ophthalmologist	Focuses on vision problems linked to the brain.
Neurologist	Evaluates brain conditions such as stroke or tumors.
Primary Healthcare Provider	Coordinates care and referrals.