Graves’ eye disease is an eye condition that occurs in about 50% of patients who currently have, or have had Graves’ hyperthyroidism if eyelid changes are included. The percentage is slightly higher if sensitive techniques such as orbital computed tomography are used. Such an approach is however not warranted in most patients. Approximately 10% of patients who have this eye disorder never develop hyperthyroidism. The reasons for the association of hyperthyroidism with the eye disease are not completely understood. Fortunately only 5% of patients will have a severe form.
Graves’ eye disease, like Graves’ hyperthyroidism and Hashimoto’s thyroiditis, is an autoimmune disorder. It is caused by the reaction of antibodies and certain white blood cells called lymphocytes, with proteins in eye muscle, the connective tissue and fat around the eyeball. This condition must be distinguished from the mild eye signs of "poppy" eyes and spasm of the eye lids which occur in most hyperthyroid patients due to an effect of excessive thyroid hormones.
The characteristic symptoms of Graves’ eye disease feature the inflammation of the eye tissues. The eyes are painful, red and watery - particularly in sunshine or wind. The covering of the eye is inflamed and swollen.
The lids and tissues around the eyes are swollen with fluid. The eyeballs bulge out of their sockets. Because of eye muscle swelling, the eyes are unable to move normally and there may be blurred or double vision. Some patients have decreased colour vision as well.
On examination, it can be seen that the eyes are pushed out of their sockets. This can be measured using an instrument called an "exophthalomometer."
There are no tests presently available to confirm specifically the diagnosis of Graves’ eye disease. The same antibodies as those of Graves’ hyperthyroidism serve as a marker for this disease.
The eye changes tend to "burn out" within a period of about 24 months and, in most cases, there is a satisfactory end result even without any treatment. The double vision and the bulginess usually do not disappear completely. Many patients are worried by the cosmetic appearance of their swollen, bulgy eyes, whereas others, with less severe defects, are inconvenienced by their inability to read clearly because of double vision. The impact of the eye disease also depends on the age, sex, and occupation of the patient. Smoking is a risk factor for more severe disease and patients are strongly encouraged to stop.
Unfortunately, there is no satisfactory treatment. Because hyperthyroidism seems to influence the eye disease, it is very important to treat the hyperthyroidism quickly and effectively but to avoid hypothyroidism, which also harms the eyes. In most patients, the eyes tend to get somewhat better when the thyroid abnormality has been treated.
In a few patients, the condition progresses regardless of what is done to the thyroid gland. These patients must be treated with strong drugs such as steroids or immunosuppressive drugs to prevent the unlikely occurrence of optic nerve swelling and blindness. Currently, intravenous corticosteroids are favoured over oral administration of this type of medication because they are more effective and have fewer side effects. If these measures do not work, it may be necessary to relieve pressure in the orbit by removing part of the tissue either by operation or by treating the eyes with external beam radiotherapy (X-rays). Both treatments reduce the pressure on the eyeball and the surrounding orbital tissues and prevent permanent optic nerve damage.
Long Term Management
Patients who have not had thyroid disease previously must be examined on a regular basis in case they develop thyroid disease. Patients with eye disease who have had their hyperthyroidism treated previously should also be examined at regular intervals to make certain that thyroid function remains normal since recurrence of hyperthyroidism, or development of hypothyroidism, may cause the eye disease to flare up. In some cases, cosmetic surgery for the eye or surgery to correct the double vision is performed. The patient is hyperthyroid at first and may have the same symptoms as patients with Graves’ hyperthyroidism, but then goes through a hypothyroid phase before full recovery. The presence of thyroid antibodies, similar to those seen in Hashimoto’s thyroiditis, is a risk factor for the persistence of hypothyroidism.