Why an MRI?
While signs and symptoms might lead a doctor to form a medical opinion, tests and diagnostic equipment are necessary to confirm and make a definitive diagnosis. Following a thorough eye exam, your doctor may recommend a magnetic resonance imaging scan, better known as an MRI. MRIs are used to look for anything that can be causing your symptoms such as a tumor near the eye or fluid putting pressure on the eye. An MRI is just one of many pieces of diagnostic imaging equipment at a doctor's disposal to confirm a diagnosis.
Understanding the Technology
An MRI scan is able to provide detailed imagery of your eye's soft tissues using a computer, radio waves and magnets. A strong magnetic field is created by passing an electrical current through wire loops, while magnet coils are simultaneously sending and receiving radio waves to get your body's protons to align themselves. When your eye's protons become aligned, they will absorb the radio waves and begin to release energy and emit energy signals. These signals that are picked up by the coil and read by the MRI's computer.
The signals form a pattern of what your eye tissue looks like, and the computer translates it into a three-dimensional image that your doctor can properly understand.
Understanding the Process
Prior to beginning the scan, a contrast dye called gadolinium is injected into your vein and eventually reaches your eye's blood vessels. This contrast dye helps the MRI form a sharper, more detailed image.
During an MRI scan, your head (and possibly your body based on the type of MRI machine at your doctor's disposal) will be placed inside a large cylindrical tube that will make loud buzzing and knocking noises as the magnets are turned on and off. While the procedure does not hurt in any way, patience is certainly a virtue as the exam may take as long as an hour to complete.
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