There are several problems which may occur depending on which areas of the brain have been affected by the stroke. Often the eye is entirely normal but the problem has happened within the brain.
Look at the diagram. Notice how the visual pathway from the optic nerve crosses over within the brain. Damage to one of the optic nerves will affect vision in one eye only. Damage beyond the crossover can affect the vision in both eyes.
The back of the brain is where information from the visual pathway is processed and images are received and understood.