Thyroid eye disease
Thyroid eye disease
Description, Causes and Risk Factors:
The thyroid gland is located at the base of the front of the neck below the larynx ("voice box"). It absorbs iodine from the blood and produces two hormones, thyroxine and triiodothyronine. It plays an important role in regulating body metabolism.
Thyroid eye disease is an `autoimmune condition. `Autoimmune' means that your own white blood cells or antibodies are causing damage to parts of your own body in addition to their normal role of protecting you against infections. In the case of thyroid eye disease, the damage is directed to fatty tissue behind the eye. Swelling of the damaged tissues behind the eyes can cause the eyes to become red and swelling to occur above and below the eyes. It may also cause the eyes to be pushed forward (`starey eyes', `proptosis'). In more severe cases, the damage at the back of the eye causes swelling and stiffness of the muscles that move the eye, causing double vision especially when you look from side to side, as the muscles cannot keep the eyes exactly in line with each other. Occasionally, the swelling behind the eyes is bad enough to press on the nerve from the eyes to the brain affecting your vision.
Although thyroid eye disorders occur at any age, the average age at onset is 45 years. There are three times as many females with thyroid eye disorders.
The exact cause do not know yet. One theory is that it follows infection with a virus that has molecules which look to the body very like the ones behind the eye. The body then makes antibodies and white cells to get rid of the virus but the reaction spills over onto the cells behind the eye. The body successfully removes the virus but is left with an `autoimmune' reaction against the eye which continues. This remains just a theory as the virus, if there is one, has not yet been found. However, we do know that thyroid eye disease, as its name suggests, is closely connected with autoimmune thyroid disease and that it is more likely to happen in smokers. It has only a slight tendency to run in families.
The commonest symptoms are mild soreness and grittiness of the eyes. Surprisingly, one eye isusually affected more than the other. There may also be increased watering of the eyes, a dislikeof bright lights and a feeling of discomfort behind the eyes especially when looking up or side-to-side. Puffiness of the upper eyelid or around the eyes (`baggy eyes') is also common and is worstfirst thing in the morning. The eyes often appear `starey' and drying of the eyes or too much tearscan cause blurry vision, which may come and go. You should consult a specialist urgently if yourvision is getting worse all the time, rather than just on and off.
Diagnosis can be made simply on examining your eyes if you already have a diagnosis of a thyroid gland problem.
Blood tests: Sometimes, blood tests are needed to back up the diagnosis. They look at how well the thyroid gland is functioning by measuring its hormones in your bloodstream. These are called thyroid function tests (TFTs). More specialized blood tests can be done to measure the antibodies in your blood.
Scans: Occasionally, thyroid scans need to be done to see how actively it is working (uptake scans). If the doctors are particularly concerned about the swelling in the orbit, they may organize a scan (known as an MRI) which will show up which tissues have been most affected.
Other tests: Doctors will want to assess your general sight carefully, including how well you see colors and how good your peripheral vision is (the vision out of the corner of your eye). They may also want to carry out an eye movement test to see how much the muscles have been affected. These assessments will be repeated throughout the course of the disease.
If a thyroid disorder is suspected, appropriate evaluation and treatment are indicated. The first priority is to restore the euthyroid condition. Sometimes the eye problems continue to progress even after the thyroid abnormality is returned to normal. Eye problems should be evaluated and treated by an ophthalmologist.
There are typically two phases of eye treatment for thyroid eye disorders. The first phase involves treating the active eye disease and focuses on preserving sight. Cornea drying/exposure often require frequent application of artificial tears, tear duct plugs or taping the eyelids shut at night. Diplopia is treated with prism in spectacles and/or patching one eye. Potentially sight threatening compression of the optic nerve may require orbital decompression surgery. Removal of portions of orbital bones creates more "space" in the orbit, relieving compression on the optic nerve while reducing proptosis. Radiation of the orbit or high doses of anti-inflammatory steroids can also sometimes utilized for the initial, acute phase of orbital swelling. The active period, which may last up to several years, requires careful monitoring until this phase stabilizes.
The second phase of treatment involves correction of stable, non-changing fibrotic changes of periocular tissue which include proptosis, strabismus (causing double vision), and eyelid retraction. Orbital decompression surgery is sometimes performed to address disfiguring proptosis, even if vision is not compromised. Because decompression surgery can alter/create strabismus and/or change eyelid position, it is preferable to perform decompression surgery before strabismus or eyelid surgery.
Stable diplopia can be improved with prism spectacles (small misalignment) and/or surgery if the strabismus misalignment is larger. Strabismus surgery involves repositioning fibrotic eye muscle/s to better align the eyes.
Eyelid retraction can be improved with surgery that relaxes eyelid muscles and/or inserts spacer material to reposition the eyelid. Eyelid surgery is best performed after decompression and/or strabismus surgery.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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