MRI stands for magnetic resonance imaging. An MRI uses a large magnet and radio fields to view the interior body. MRI is particularly good at imaging soft tissues like the brain, but has limited use for looking at the eye itself. Some scientists estimate that a third of the brain is involved with vision in some way. Therefore, we obtain an MRI in cases of unexplained visual field loss or with cranial nerve palsies to look for tumors, mass lesions, and signs of stroke.