Hemianopie

Hemianopia, also known as hemianopsia, is a loss of half of the visual field in one or both eyes. The most common form is homonymous hemianopia, in which the same side of the visual field is lost in both eyes due to a lesion behind the optic chiasm (retrochiasmal pathway), such as the optic tract, optic radiations, or occipital cortex. A less common form is heteronymous or bitemporal hemianopia, typically caused by lesions at the optic chiasm that affect crossing nasal fibers.

Causes and clinical presentation

The most frequent cause of homonymous hemianopia in adults is stroke, followed by brain tumors, traumatic brain injury, and demyelinating diseases. The defect is usually complete for one half of the field, though central or macular sparing can occur when the occipital cortex representation is asymmetric. Patients may be unaware of the deficit (visual field neglect) and report bumping into objects or difficulties with reading, driving, and mobility. Pupillary light reflexes are typically preserved because the defect lies behind the optic chiasm and the afferent pathways to both pupils can remain intact.

Diagnosis and imaging

Diagnosis relies on formal visual field testing (perimetry) to map the defect, along with clinical confrontation tests. Imaging, primarily magnetic resonance imaging (MRI) of the brain, is used to identify the underlying lesion and its location. Computed tomography (CT) may be employed in acute settings.

Management and prognosis

Management focuses on treating the underlying cause (for example, acute stroke management or tumor-directed therapy). Visual rehabilitation and compensatory strategies, such as scanning training and, in some cases, prism glasses, can help patients cope with field loss. Prognosis varies with the cause and extent of brain injury; some patients experience partial recovery, especially in the first months after onset, while others have persistent deficits.