Introduction

Thyroid eye disease is an inflammatory condition that involves the orbit of the eye. Thyroid eye disease may also be called thyroid-associated ophthalmopathy (TAO), thyroid orbitopathy, Graves’ orbitopathy or Graves’ ophthalmopathy (GO). This condition affects a lot of aspects of the eye including; the eye socket, fat cells ( adipocytes), muscles that control the movement of the eye (extraocular muscles) and fibroblasts which are connective tissue cells. The optic nerve and the blood vessels that supply the area of the eye are also affected by this inflammatory disease.¹ There are varying symptoms of thyroid eye disease with differing extremities, ranging from a singular dry eye to serious loss of sight in both eyes.² Moreover, there are many factors that affect the long-term outcomes of this disease, with this article aiming to explore the factors that determine the outcomes in patients.

How does Thyroid Eye Disease develop?

The exact causes of Thyroid eye disease are still being researched, however, there is an understanding that the mechanism is due to the body creating antibodies to TSH (thyroid-stimulating hormone) receptors leading to inflammation. This receptor is not only found in the thyroid gland but is also present in many other body tissues, including the tissues that surround the eyes. There are usually two separate phases in the progression of Thyroid Eye disease. Firstly, there is an active or progressive phase where there is inflammation of the tissues in the eye. This active stage usually lasts from about six months to two years and this is dependent on the individual. Once the swelling settles down, there is a new stage called the inactive phase. In the inactive phase, although the active inflammation may subside, scarring may still persist and this can lead to long-term changes to the appearance of the eye and also eye function.³

The outcomes of Thyroid Eye Disease, including long-term outcomes 

Some of the less severe symptoms of Thyroid Eye Disease are eyelid swelling, eyelid retraction (this is when the upper eyelid is raised more than it normally should be), dry eyes, bulging eyes and diplopia (double vision). The more severe outcomes of thyroid eye disease include a change in the visual field, blurred vision, change in colours, and a dimming of sight. There is also the potential risk of permanent vision loss. In the vast majority of cases, people diagnosed with Thyroid Eye Disease only experience mild symptoms - most patients only report dry eyes which can easily be managed using lubricating eye drops.⁴

However, for some people, Thyroid eye disease can end up negatively altering their lives. This is due to vision changes impacting their ability to carry out their usual activities; they may be forced to quit their hobbies, or more drastically even their job. Other day-to-day activities that can be impacted include reading and being able to drive.⁵ This can have severe impacts on the quality of life for patients, as they may struggle to live independently. However, Health assessments focused on the long term impacts of Thyroid Eye Disease showed that patients continued to have vision impairments and concerns about their appearance, even years after the disease had stopped progressing.¹⁴

Thyroid Eye Disease can also have detrimental effects on the mental health of patients suffering from the disease. The visible symptoms of Thyroid Eye Disease can lead to increased anxiousness surrounding self-esteem and social interactions. Moreover, the chronic nature of the disease can lead to feelings of hopelessness as individuals may not be able to take part in activities that they previously enjoyed and this can spiral into depression in the long term.¹⁴

What are the factors that affect the progression of Thyroid Eye Disease?

There are many factors that are associated with increased severity of Thyroid Eye Disease. Patients with hyperthyroidism are more likely to experience a more severe progression of Thyroid Eye Disease compared to patients with hypothyroidism. In more severe cases where the patient also suffers from Graves disease ( an autoimmune disorder that can cause hyperthyroidism or an overactive thyroid) there are recommendations against receiving radioactive iodine treatment in order to help prevent Thyroid Eye Disease from getting worse.⁶ Moreover, more severe disease progression has been linked to the presence of diabetes mellitus in patient.⁷ There are several other diseases that are associated with a more aggressive presentation of Thyroid Eye Disease and these include high blood pressure, depression, anxiety and non-thyroidal autoimmune diseases.¹⁰ 

Direct or indirect smoking increases the risk of developing worsening thyroid eye disease (TED) and reduces the effectiveness of treatment. The more cigarettes a person smokes each day, the higher the risk.⁸

The factors affecting recovery

There are many different types of treatments for Thyroid eye disease, and the type of treatment affects the nature of recovery for patients. Corticosteroids are commonly used to reduce inflammation during the active phase of the disease and whilst they are effective in the short term, their benefits may not be sustained, and long-term use of corticosteroids can lead to harmful side effects. Another treatment form that has varying recovery rates for patients is radiotherapy, as although it can also help to reduce inflammation it also comes with risks to the patient. Following radiotherapy, the time taken to see an improvement in thyroid eye disease varies from person to person - with some having to wait up to a year to notice the full effect of the treatment.¹² Radiotherapy also has a greater effect if the patient is a nonsmoker. 

There are also many side effects of radiotherapy that can impact recovery such as fatigue and skin reactions. If the patient is diabetic or has high blood pressure and undergoes radiotherapy to treat Thyroid eye disease, they are at a greater ( but still very small) risk of having changes to the back of the retina that can disturb vision. Moreover, there is a small risk of developing long-term dry eyes.¹³ These are just a few examples of how the specific treatment pathway used has an effect on the recovery of the patient, alongside the different comorbidities and health factors that also have an impact.

Early diagnosis of thyroid eye disease can improve prognosis and recovery from some of the symptoms of the disease. If double vision is more severe and persistent, doctors may try steroids, radiation therapy, or other types of medications to try and alleviate eye muscle irritation and swelling. The best time to begin these treatments is within the first three to six months after the onset of symptoms. Surgery might be required to realign the eye muscles and help the eyes line up properly again, though, if double vision becomes chronic and medication is ineffective.⁹

This emphasises the importance of identifying symptoms and tailoring treatment strategies at an early stage and the effect it can have on recovery of symptoms. Patients have a good chance of recovering all of their lost vision if the condition is identified early and treated appropriately. Seeking medical attention as soon as possible helps avoid long-term eye damage and improves the chance of a full recovery. Another example of treatments that are more efficient if used earlier on in disease progression are corticosteroids and teprotumumab which have a “critical window” with the highest efficiency in the first 6 months of the disease; after this, there is a 20% to 30% reduction in their outcomes.¹⁰

Sufficient intake of nutrients such as selenium and vitamin D can also support thyroid function and influence immune responses, potentially influencing Thyroid Eye Disease progression and recovery.¹¹

Summary

To conclude, Thyroid Eye Disease (TED) is a complex inflammatory disease that affects not only affect eyes but the general life of a patient as well. The majority of patients have only minor symptoms that can be treated properly, while some experience severe complications that lead to vision impairment, cosmetic issues, and psychosocial distress. There are many factors that can impact the prognosis and recovery of patients with Thyroid Eye Disease. Early identification of the disease, rapid intervention, and effective treatment approaches are key to the prognosis of Thyroid Eye Disease. Generally speaking, early treatment increases the chance that patients will avoid serious long-term complications and maintain their vision. Lifestyle choices like quitting smoking, eating a healthy diet and controlling thyroid hormones can also have a big impact on how well a patient recovers from their illness.