An optical coherence tomography (OCT) test is completely different from a magnetic imaging resonance (MRI) test. During an OCT, you simply sit on a chair, and you're asked to look into the device as it takes a photograph of your eye. For an MRI, you must lie down in a large tube, and then the scan uses radio waves and strong magnetic fields to produce the required images. Although both tests provide detailed imaging, the OCT takes images of cross-sections of the retina, while the MRI scan can take pictures of any part of the body.