Glossary of Terms

Reviewed by: HU Medical Review Board



Antibodies are chemicals that the body makes to fight infection, germs, or cancer. If a person has an autoimmune disease, the person’s antibodies are mistakenly attacking healthy cells and tissue.1

Autoimmune disease

A disease in which the immune system attacks the body’s healthy cells and tissues by mistake. In TED, the body’s immune system attacks healthy cells around and behind the eye.2


Chemosis (key-moe-sis)

Swelling of the clear tissue that lines the eye and eyelids. Chemosis can occur in the active (acute) phase of TED.3


Diplopia (dih-ploh-pee-uh)

Double vision, or seeing 2 of 1 object. Diplopia can occur from TED when the muscles around the eye are affected.4


Exophthalmos (ek-sof-thal-muhs)

Also known as proptosis (prop-toe-sis), exophthalmos is when the eyeball protrudes or bulges out of the bony eye socket.4

Exophthalmometer (ek-sof-thul-mom-i-ter)

A special ruler-like device an eye doctor or TED specialist uses to measure the amount of eye protrusion within the bony eye socket. In TED, bulging eyes are common because of swelling behind and around the eye.4

Eyelid retraction (lateral flare)

Eyelid retraction, or lateral flare, occurs when the eyelids and muscles around the eyelids swell, making it difficult to blink. Retracted eyelids look pulled back and swollen, which is a common symptom in TED.4


Graves’ disease

An autoimmune disease where abnormal immune cells attack the thyroid gland. The thyroid responds by making an excessive amount of thyroid hormone. Too much thyroid hormone leads to an overactive thyroid (hyperthyroidism). Graves’ is the most common cause of hyperthyroidism that may lead to symptoms of TED.5,6

Graves’ eye disease

Another name for thyroid eye disease.7

Graves’ ophthalmopathy (GO)

Another name for thyroid eye disease.7

Graves’ orbitopathy

Another name for thyroid eye disease.7


Hashimoto’s disease

An autoimmune disease where the body’s immune system attacks the thyroid gland, leading to an underactive thyroid (hypothyroidism). Hashimoto’s disease is the most common cause of hypothyroidism and may lead to symptoms of TED.8


Underactive thyroid, which is when your thyroid does not make enough thyroid hormone. Thyroid eye disease can occur in those with hypothyroidism.9


Overactive thyroid, which is when your thyroid gland produces too much thyroid hormone thyroxine. Hyperthyroidism is common in those with TED.10

Thyroid-associated ophthalmopathy (TAO)

Another name for thyroid eye disease.7


Optic nerve compression

Known as optic neuropathy, optic nerve compression is when the optic nerve of the eye is squeezed (compressed) because of swelling or an injury inside or near the back of the eye orbit. Because the optic nerve is the communication highway for the eye and brain, problems with the optic nerve can be sight-threatening and lead to vision loss if not treated quickly.11


Proptosis (prop-toe-sis)

A stare-like glance or bulging eyes, proptosis in TED occurs as a result of swelling of the fat and tissues around and behind the eyes. Also known as exophthalmos (ek-sof-thal-muhs).4


TED often leads to light sensitivity or a painful reaction to light, known as photophobia. Photophobia usually occurs as a result of an irregular, dry eye surface that can cause light to scatter in many directions. The scattered light can cause discomfort and pain. In contrast, a smooth, moist eye surface focuses light without scattering.12-14

Prism lenses

Prism lenses are special lenses placed in eyeglasses that bend light before it reaches the eye. When the light is redirected, it reaches the retina in the right spot to allow the brain to make a single, clear image. In TED, double vision may occur, and prism lenses might help.15


Strabismus (struh-biz-mus)

Misalignment of the eyes or looking “crossed-eyed” when your eyes do not line up normally. Because TED can attack the muscles of the eye responsible for eye movement, strabismus can occur.4



Your thyroid is a gland located at the bottom of your neck, just below your Adam’s apple. The thyroid releases thyroid hormones, which play an important role in nearly every body function. The main job of the thyroid gland is metabolism or the speed at which your cells work.16

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