Thyroid Eye Disease
What are the symptoms?
Most patients start to notice eye problems at the same time as the onset of their thyroid problem. For some patients, thyroid eye disease may develop some years either before or after the onset of the actual hormone imbalance. When TED starts to become apparent, most patients are hyperthyroid, with a smaller proportion euthyroid (normal thyroid activity) or hypothyroid (underactive thyroid activity).
Both eyes are usually affected, although the severity of disease may differ dramatically between left and right. Classically, TED is described to go through different cycles, with an active phase (characterised by orbital inflammation), a static phase (characterised by no change in activity) and burnt out phase (when there is no longer any signs of activity) with patient’s symptoms and signs reflecting the current phase. How long each phase lasts and the severity of each phase varies from patient to patient.
During the active phase, patients often notice the sensation of pressure around the eyes with irritation, redness and tearing. Inflammation of the structures around the eye also causes the same structures to become scarred. Inflammation of the fat and muscles around the eye cause their enlargement, resulting in the eye being pushed forward and the sensation of pain in different positions of gaze as the muscles become stretched. If the muscles become too swollen, the enlarged muscles can compress the optic nerve (the main nerve which takes information from the eye to the brain) resulting in blurring/ loss of vision.
After several months, as the active inflammation starts to wear off (static phase), the patient’s eyes feel less wet and inflamed. Eventually the inflammation disappears completely and the previously engorged swollen soft tissues start to shrink back to normal size (burnt out phase). However, any scarring, which developed when the TED was active, remains. Scarring of any structure means that it becomes less able to stretch.
For example, the muscles which control the position of the gaze of the eye may have become scarred, leading to double vision.
Similarly, scarring of main tendon involved in controlling the movement the upper lid, may result in an inability for the upper lid to descend properly, resulting in a staring appearance (upper lid retraction). Sometimes this may be so severe that the cornea may become dry from overexposure.
Many patients will be left with some degree of protrusion of the eye itself, lid retraction, or double vision that may require additional treatment.
Is thyroid eye disease serious?
Thyroid eye disease if severe enough can threaten sight. Increased exposure of the cornea from eyeball protrusion or lid retraction can lead to corneal scarring. Double vision can be severe and disabling. If the swelling is severe enough, the pressure in the orbit (eye socket) can become extremely high and compress the optic nerve. The person may experience progressive loss of vision, and possibly blindness if the condition is not treated promptly. However, it must be stressed that most patients with TED suffer only a mild short lived form. Only a small proportion of patients develop the severe, sight threatening type.
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