How can tell the difference between spatial neglect and hemianopia?

These. Are visual abnormalities that result from a brain injury, most often a stroke. Hemianopia means that there is no vision on half of the normal visual field - this is always on the left or right side. Neglect is an unusual symptom in which the vision is present but is ignored by the person. People who have this will not see anything unless it is pointed out to them.