Scientists say they have solved the mystery of how a girl with half a brain has near perfect vision in one eye.

A 10-year-old girl born with half a brain, from Germany, has the power of both a right and left eye in the single organ in the only known case of its kind in the world.

Scans revealed the German girl’s brain rewired itself during development when she was still in her mother’s womb.

The girl’s underdeveloped brain was discovered when, aged three, she underwent an MRI scan after suffering seizures of brief involuntary twitching on her left side.

Apart from the seizures, which were successfully treated, and slight weakness on her left side, the girl has had a normal medical history, attending school and taking part in regular activities.

In other cases, where patients have half of the brain removed to treat severe epilepsy, for example, one field of vision is lost in both eyes, meaning they see only objects on the left or right side of their vision.

In the case of the German girl, her left and right field vision is almost perfect in one eye.

"The brain has amazing plasticity but we were quite astonished to see just how well the single hemisphere of the brain in this girl has adapted to compensate for the missing half", said Dr. Lars Muckli, lead researcher of the University’s Centre for Cognitive Neuroimaging.

Scans on the girl showed that the retinal nerve fibres carrying visual information from the back of the eye which should have gone to the right hemisphere of the brain diverted to the left. The understanding of the powerful algorithms the brain uses to rewire itself could help advance artificial intelligence work.