Because thyroid eye disease (TED) can cause a wide variety of signs and symptoms, doctors use different exams and tests to diagnose and monitor the condition. TED symptoms, such as vision changes, pain, and inflammation, can also be caused by a number of conditions. Doctors and TED specialists may use several tests to rule out other conditions before determining a diagnosis of TED.1
After taking your medical and symptom history, your TED doctor may recommend imaging tests, including CT and MRI scans. Imaging exams of your eyes and face are used to diagnose TED and monitor the severity or progression of the disease. These tests are also used along with other exams and tests to help manage TED.1,2
CT scan
A computed tomography (CT) scan, also called a CAT scan, is a type of imaging tool that uses special X-ray equipment to create cross-sectional views of the inside of the body. A CT scan may be used in the diagnosis of TED or to see progressive (worsening) changes caused by TED.2
MRI
Magnetic resonance imaging (MRI) is a common tool for diagnosing TED. MRI machines use a powerful magnet and radio waves to take an image of the inside of the body. Unlike CT scans, MRI does not use any radiation. This makes it a helpful imaging tool for people who should not receive radiation, such as children or people who are pregnant.3
The images created by MRI are very clear. However, they take longer to complete. X-rays and CT scans take seconds to minutes to finish. MRIs can take many minutes to an hour or longer depending on the part of the body imaged.3
An MRI machine has a tube-like opening you will be guided into. How far you are placed inside the tube depends on the area of the body your doctor wants to be scanned. If you are uncomfortable in enclosed spaces, tell your doctor or the MRI technician before your scan. Some facilities have open MRI machines that reduce the feeling of being enclosed. If needed, your doctor can give you medicine before the MRI to help you relax.3
CT and MRI findings in TED
In the case of TED, a CT or MRI scan of the orbits (bony eye sockets) would show some abnormalities, such as:2,4,5
- Swelling of the muscles that attach to the eye (extraocular muscles)
- Damage to the bundle of nerves in the eye known as the optic nerve (optic neuropathy)
- Choroidal folds, which are lines in the layer of the eye with many blood vessels (known as the choroid). The choroid layer provides the outer layers of the retina of the eye with nutrition and oxygen. Choroidal folds may be harmless, or they could lead to decreased vision.
- Orbital fat swelling (fat behind the eye)
- Inflammation of the eye tissues
Conventional X-ray is not useful in diagnosing TED because bone abnormality that is found on X-ray does not usually occur in TED. MRI and CT scans show abnormalities of soft tissue, muscles, nerves, and fat, which are common in TED.2
Your TED specialist, an eye doctor specializing in the diagnosis and treatment of TED, might have other tests they recommend.2
