- 1.
What is thyroid eye disease?
Thyroid eye disease (TED) is a chronic inflammatory disease of the orbits that occurs most often in patients with a systemic thyroid imbalance. Chronic inflammation results in scarring and dysfunction of the orbit. The course and severity are variable.
- 2.
Who is at risk for thyroid eye disease?
TED occurs in a wide range of ages. It has been reported from 8 to 88 years of age, with the average age of onset in the forties. Females are affected three to six times more often than males. Children are rarely affected.
- 3.
Is everyone with thyroid eye disease hyperthyroid?
Ninety percent of patients who develop TED have Graves’ hyperthyroidism, 3% have Hashimoto thyroiditis, 1% have primary hypothyroidism, and 6% are euthyroid. As many as one-third of patients do not develop clinical hyperthyroidism for more than 6 months after the onset of symptoms of TED. Thus, a significant number of patients who present with TED have not yet developed hyperthyroidism.
- 4.
What causes thyroid eye disease?
We do not know. TED is an immune-mediated process with the primary target the orbital fibroblast. Many theories link the orbit and thyroid gland by a shared antigen, the thyroid-stimulating hormone receptor. Research continues to try to better understand TED.
- 5.
Do environmental factors affect thyroid eye disease?
Smoking is the one environmental factor that has been shown to affect TED. Multiple studies have shown a higher incidence of smoking in patients with TED than in patients with Graves’ disease who do not have TED. Research suggests that smokers with TED have more severe disease and the disease lasts longer than in nonsmokers. The effects of secondhand smoke can only be speculated on.
- 6.
Does thyroid eye disease improve when the systemic thyroid imbalance is treated?
Treatment of the systemic thyroid dysfunction has little predictable effect on the course of TED. Posttreatment hypothyroidism may worsen TED, especially if the hypothyroidism is profound. Also debated is whether radioactive iodine (RAI), surgery, and medical treatment have different effects on the course of TED. A large study suggested that treatment with radioactive iodine has a greater chance of causing progression of TED. The study also showed that giving systemic steroids during the treatment decreases and may eliminate this risk.
- 7.
Should all patients who receive radioactive iodine be treated with systemic steroids?
Unless the patient has specific contraindications or until further studies show otherwise, we recommend that patients undergoing radioactive iodine treatment receive a course of systemic steroids. The dosage and length of treatment are controversial. The patients at the highest risk of worsening TED with RAI are smokers and patients with active disease.
- 8.
What are the early signs of thyroid eye disease?
Many patients initially present with intermittent eyelid swelling along with nonspecific ocular irritation, redness, and swelling ( Fig. 35-1 ). Because all of these symptoms are nonspecific, early-onset TED is infrequently diagnosed. The disease is not recognized until the appearance of more obvious clinical signs, such as eyelid retraction, eyelid lag, or early proptosis ( Fig. 35-2 ). Suspecting TED in patients with the aforementioned nonspecific symptoms is important, especially if they have symptoms or history of a thyroid imbalance.
Figure 35-1
Early thyroid eye disease with mild eyelid retraction of the left upper eyelid and the right lower eyelid.
Figure 35-2
Thyroid eye disease with proptosis and eyelid retraction.
- 9.
What studies need to be done in the workup for thyroid eye disease?
The most effective screening tool for systemic thyroid imbalance in patients with TED is the level of thyroid-stimulating hormone. An internist or endocrinologist can do further evaluation and workup. Patients require a complete ophthalmic exam. Special attention should be paid to visual function, including acuity, pupils, color vision, and, if indicated, visual fields. In particular, the ophthalmic exam should include noting eyelid position, evaluation of ocular motility with note of any diplopia, and checking for corneal exposure and proptosis.
- 10.
Which patients require orbital imaging?
Not all patients with TED require orbital imaging. Indications for imaging include suspicion of optic nerve compression, evaluation for orbital decompression surgery and/or orbital irradiation, unclear diagnosis, and a need to rule out other orbital processes. We prefer a computed tomographic scan without contrast in patients with thyroid-related ophthalmopathy who require imaging.
- 11.
What findings are present on orbital imaging?
The classic finding is enlargement of the rectus muscle belly with sparing of the tendon ( Fig. 35-3 ). The inferior rectus is the most commonly involved muscle, followed by the medial rectus and the superior rectus. The lateral rectus is least likely to be involved.
