Understanding Hemianopia: Causes, Types, and Treatments
Visual field impairment: Characteristics, sources, determination, remedy
Hemianopia is a visual condition characterised by the loss of half of the visual field in one or both eyes. This loss can significantly impact a person's daily life, driving abilities, and navigation skills. The causes and types of hemianopia vary, and understanding them is crucial for early diagnosis and effective treatment.
Common Types of Hemianopia and Their Causes
Hemianopia can be categorised into several types, each corresponding to different locations of lesions along the visual pathway.
- Bitemporal Hemianopia is characterised by the loss of the outer (temporal) halves of both visual fields. Common causes include compression at the optic chiasm, typically by tumours near the pituitary gland such as pituitary adenomas, craniopharyngiomas, and meningiomas.
- Homonymous Hemianopia results in the loss of the same half (left or right) of the visual field in both eyes. This type is often caused by lesions behind the optic chiasm, such as stroke, brain tumours, traumatic brain injuries, or multiple sclerosis affecting the optic tract, lateral geniculate body, or occipital cortex.
- Junctional Scotoma (Including Junctional Scotoma of Traquair) involves visual field defects at the junction of the optic nerve and optic chiasm. This type is usually due to sellar masses like pituitary tumours compressing the optic nerve-chiasm junction.
Treatments by Cause
Treatment for hemianopia often involves addressing the underlying cause of the condition.
- Tumours causing compressive hemianopia (e.g., bitemporal hemianopia from pituitary adenoma): Surgical decompression is typically required to remove or reduce tumour size. Adjunct therapies may include hormone therapy or radiotherapy depending on tumour type.
- Stroke or cerebrovascular causes (homonymous hemianopia): Immediate management of stroke is critical (e.g., thrombolysis, controlling risk factors). Vision rehabilitation therapy can improve adaptation and coping.
- Inflammatory or infectious causes: Treatment with corticosteroids or appropriate antimicrobials.
- Optic nerve/tract damage from toxic, nutritional, or retinal diseases: Correction of the underlying cause may improve vision if addressed early (e.g., removing offending drugs, nutritional supplementation).
- Vision Rehabilitation and Compensatory Strategies: Regardless of cause, many patients benefit from vision therapy to train eye movements, use of prisms, and occupational therapy to adapt daily activities.
Summary
Understanding the types of hemianopia and their causes is essential for effective treatment. Bitemporal hemianopia is mainly caused by tumours at the optic chiasm, especially pituitary tumours, and treated by surgical decompression. Homonymous hemianopia results from post-chiasmal lesions such as stroke or tumours and focuses on treating the primary neurological condition plus rehabilitation. Junctional scotomas arise from lesions at the optic nerve-optic chiasm junction, often due to sellar masses, treated surgically or medically depending on etiology. Early diagnosis and addressing the underlying cause are critical for preserving or improving vision.
- Bitemporal hemianopia, often caused by tumors like pituitary adenomas or craniopharyngiomas compressing the optic chiasm, may be treated through surgical decompression to remove or reduce tumor size, with additional therapies such as hormone therapy or radiotherapy.
- Homonymous hemianopia, resulting from post-chiasmal lesions like stroke, brain tumors, or multiple sclerosis, focuses on treating the primary neurological condition and improving adaptation and coping through vision rehabilitation therapy.
- Junctional scotomas, caused by lesions at the optic nerve-optic chiasm junction, are often due to sellar masses like pituitary tumors, and they can be treated surgically or medically depending on the etiology, with vision rehabilitation and compensatory strategies always being beneficial for many patients.
