Exophthalmos describes a condition where the eyeball protrudes from the eye socket, making it appear to bulge. It can affect one or both eyes.
Depending on how severe it is, exophthalmos can cause eye problems such as corneal dryness and conjunctivitis, which is an inflammation of the membrane lining the eye.
In the long-term, symptoms tend to improve, but this can take years. There is a possibility that the eyes may continue to bulge if treatment is not received.
Exophthalmos is not a condition, but the sign of a disorder. Commonly, it can signal a problem with the thyroid gland. Graves’ disease is the most common cause of exophthalmos.
Graves’ disease and thyroid disorders
Graves’ disease affects the thyroid gland.
Graves’ disease is an autoimmune disease that causes hyperthyroidism. A person with hyperthyroidism has an overactive thyroid gland that produces excess hormones and causes it to grow.
The thyroid is in the neck, below the Adam’s apple. The hormones it produces help to regulate growth, the rate of metabolism and other important functions of the body. The hormones are called thyroxine and triiodothyronine, and they are normally kept in balance.
Thyroid eye disease is a condition where the soft tissues and muscles around the eyes become swollen and inflamed.
It is often due to hyperthyroidism, and sometimes to hypothyroidism, which is caused by an underactive thyroid gland.
Hyperthyroidism or hypothyroidism may not cause the eyes to protrude immediately. It may take some time for this to happen.
In a healthy person, the immune system attacks pathogens, the organisms and substances that are bad for us. These include some bacteria, viruses, parasites, cancer cells, and fungi. However, in certain people, the immune system starts attacking normal tissue. This is described as an autoimmune reaction.
Graves’ disease is an example of such an autoimmune reaction. Experts are not sure why autoimmune diseases occur. If a person’s immune system attacks the thyroid gland, it may react by producing extra hormones.
The autoimmune antibodies can attack the muscles and soft tissue surrounding the eyes, which can cause them to protrude from the sockets.
This can lead to:
dry or gritty eyes
inflammation and swelling
Exophthalmos is a symptom of Graves’ disease.
Image credit: Jonathan Trobe, M.D, 2011
Graves’ disease is the most common cause of exophthalmos. Anywhere from 25-50 percent of people with this condition will have an eye involvement.
Interestingly, eye involvement can occur up to 10 years before the diagnosis of thyroid problems is made and up to 20 years after. The immune cells that attack the thyroid in Graves’ disease also accumulate within the eye socket. The fatty tissue and muscles around the eye become large, pushing the eye forward and out.
A person who has Graves’ exophthalmos may experience the following symptoms:
pain in the eyes
photophobia, or sensitivity to light
lacrimation, or eye secretions, and shedding of tears
diplopia, or double vision caused by weakening of the eye muscles
blindness if the optic nerve is compressed
difficulty in moving eyes, as the eye muscles are affected
feeling pressure behind and around the eyes
Other signs and symptoms of Graves’ disease not related to the eyes include irregular heartbeats, anxiety, elevated blood pressure, increased appetite, weight loss, diarrhea, and sleeping problems.
While Graves’ disease is the most common disorder that can cause the eyes to protrude it is not the only one.