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The brain is divided into two halves, each with its own blood supply. Each half is responsible for sensation, movement and vision of the opposite side of the body. Hemianopia is a blindness or reduction in vision in one half of the visual field due to damage of the optic pathways in the brain. This damage can result from acquired brain injuries caused by stroke, tumour or trauma. A stroke occurs when there is a sudden disturbance in the blood supply to the brain, either by a blockage in a blood vessel or by a haemorrhage into the brain.

A stroke may cause severe sight loss both as a result of loss of vision to one side or the other, hemianopia, and by the loss of visual awareness, so that the victim is not aware of the loss. When the loss is over a large part of the field of vision, people and objects may be missed, making day-to-day tasks such as reading and getting around difficult.

Depending on the area of the brain that is damaged, a stroke can result in coma, paralysis of one side of the body, speech and vision problems, and dementia.

Different Types of Hemianopia

The most common defect, right homonymous hemianopia, occurs in corresponding halves of the right field of vision. It can also occur in corresponding halves of the left field of vision (left homonymous Hemianopia), in the upper half of the field (superior hemianopia), the lower half (inferior hemianopia), or both outer halves of the field (bitemporal Hemianopia). In hemianopia, half of the field is blanked out on both eyes.


  • Loss of half of the field of vision
  • Decreased night vision
  • Need for more light

Risk Factors

Whoever may be at risk for stroke is also at risk for hemianopia. People with high blood pressure or those with an abnormal heart rhythm, which is associated with blood clots in the heart, may be at risk from a stroke.

Age is also a risk factor, as the majority of people who experience stroke are over the age of 55.

Reducing the Risk

Reducing the risk of stroke will reduce the risk of hemianopia. Monitor your blood pressure regularly, stop smoking, eat a sensible diet and take regular exorcise.

Disclaimer of Medical Liability

Whilst we have taken great care to gather correct information and to keep it current, we cannot guarantee its accuracy and completeness.

The information provided should never be considered a substitute for professional health care by a qualified doctor or other health care professional, which will be tailored to the patient's individual circumstances. We cannot take responsibility if you rely on this information alone.