Homonymous Hemianopia

Homonymous hemianopia is loss of half the visual field on the same side in both eyes. For example, a right homonymous hemianopia means the right half of vision is lost in both the left and right eyes. This indicates damage to the brain (not the eyes) and is most commonly caused by stroke.

Understanding the Pattern

Due to how the visual pathways are organized:

• Information from the left visual field goes to the right brain
• Information from the right visual field goes to the left brain

So damage to the right side of the brain causes left homonymous hemianopia, and vice versa.

What Patients Experience

• Missing half of the visual world
• Bumping into objects on the affected side
• Difficulty reading (especially left hemianopia)
• Getting lost in familiar places
• May not initially realize vision is abnormal
• "Where did that car/person come from?"

Causes

Stroke (Most Common)

• Posterior cerebral artery stroke—most common
• Middle cerebral artery stroke
• See Stroke and Vision

Other Causes

• Brain tumor
• Traumatic brain injury
• Brain surgery complications
• Multiple sclerosis (less common)
• Hemorrhage
• Infection or abscess

Associated Features

The specific features can help localize where in the brain the damage occurred:

Complete vs. Incomplete

• Complete: Entire half field missing
• Incomplete: Partial involvement (quadrantanopia)

Macular Sparing

• Central vision preserved
• More common with occipital lobe lesions
• May allow some reading ability

Congruence

• Congruent: Defects nearly identical in both eyes (occipital lobe)
• Incongruent: Defects differ between eyes (more anterior lesions)

Diagnosis

Visual Field Testing

• Visual field test documents the pattern
• Shows defect respecting vertical midline
• Quantifies severity

Brain Imaging

• MRI brain to identify the lesion
• CT scan if MRI not immediately available
• MRA or CTA if vascular cause suspected

Stroke Workup

If stroke is the cause:

• Cardiac evaluation
• Carotid imaging
• Blood tests for risk factors

Treatment

Acute Stroke

• Emergency stroke treatment if within time window
• tPA (clot-busting medication) if eligible
• Thrombectomy for large vessel occlusion

Rehabilitation

• Visual rehabilitation—compensatory strategies
• Scanning training—learning to look toward blind side
• Prism therapy—controversial but may help some
• Occupational therapy—adapting daily activities

Treat Underlying Cause

• Stroke prevention measures
• Tumor treatment if applicable
• Address other causes appropriately

Visual Prognosis

• Some spontaneous recovery possible (especially first 3-6 months)
• Complete recovery uncommon
• Learning to compensate is key
• Rehabilitation can improve function even without recovery

Living with Homonymous Hemianopia

Reading Difficulties

Particularly challenging with left hemianopia:

• Difficulty finding the start of lines
• Use a ruler or line guide
• Some patients benefit from reading vertically
• Large print may help

Driving

• Most jurisdictions have visual field requirements
• Usually cannot drive with complete hemianopia
• Some may qualify with incomplete defects
• Check local regulations

Safety Strategies

• Turn head actively toward blind side
• Arrange furniture to minimize obstacles
• Good lighting throughout home
• Walk with affected side toward wall
• Use a cane if needed

Technology Aids

• Text-to-speech software
• Large monitors positioned appropriately
• Apps that can help with reading

Related Conditions

• Quadrantanopia—one quarter affected
• Stroke and Vision