Hemianopsia is a visual field defect characterized by the loss of vision in one-half of the normal visual field of one or both eyes. Lesions affecting the optic tract or complete optic radiation cause homonymous hemianopsia, with the same half of the visual field lost in both eyes. Incomplete homonymous hemianopsia, affecting less than half of the visual field in each eye, often indicates occipital lobe involvement. Lesions of the optic chiasm, tract, or radiation may also impair color perception and visual processing.

Pathophysiology

Visual information from each eye is transmitted via the retina → optic nerve → optic chiasm → optic tract → lateral geniculate nucleus → optic radiation → visual cortex.

• Optic chiasm lesions: Typically cause bitemporal hemianopsia due to compression of nasal retinal fibers.

• Optic tract or radiation lesions: Cause homonymous hemianopsia (loss of the same visual field in both eyes).

• Occipital lobe lesions: Can cause incomplete homonymous hemianopsia, scotomas, or cortical blindness, often with preserved pupillary light reflex.

• Associated cerebral lesions may produce visual hallucinations, impaired color perception, or other sensory deficits.

History and Physical Examination

History

• Sudden or gradual onset of vision loss in one visual field

• Symptoms of associated neurological deficits: headache, seizures, dysarthria, facial/limb weakness, ptosis

• Past medical history: eye disorders, stroke, hypertension, diabetes, trauma, brain tumors

• Pediatric clues: failure to reach for toys, missed objects

Physical Examination

• Visual field testing: cover one eye and move an object from the periphery to the center, asking when it is first seen; repeat in all quadrants

• Assess level of consciousness, pupillary reactions, motor responses

• Evaluate for color vision loss, visual hallucinations, and associated neurologic deficits

Common medical causes

Special considerations

• Consider formal visual field testing (perimetry or tangent screen) for significant deficits

• Ensure patient safety: approach from unaffected side, remove hazards, arrange personal items within intact visual field

• Educate patient on compensatory techniques and environmental modifications

Patient counseling

• Teach strategies for scanning the environment

• Discuss safety measures to prevent falls and accidents

• For children, instruct caregivers to place objects within the child’s functional visual field

Pediatric considerations

• Brain tumors are the most common cause

• Visual field deficits may present as missed objects or difficulty reaching for toys

• Nonverbal clues are crucial for early detection

Geriatric considerations

• Evaluate for stroke, tumor, or age-related ocular pathologies

• Visual field testing, neuroimaging, and specialist consultation recommended

References

• Mack, G. S. (2011). ReNeuron and stem cells get green light for neural stem cell trials. Nature Biotechnology, 29(2), 95–97.

• Ohira, K., Furuta, T., Hioki, H., Nakamura, K. C., Kuramoto, E., Tanaka, Y., … Nakamura, S. (2010). Ischemia-induced neurogenesis of neocortical layer 1 progenitor cells. Nature Neuroscience, 13(2), 173–179.