Thyroid eye disease (TED) causes swelling and inflammation of the tissues and muscles of the eye. The result is symptoms such as pain, irritation, and pressure of the eyes and tissues around the eyes.1,2
One other symptom you may have with TED is a misalignment of the eyes or looking “crossed-eyed” when your eyes do not line up normally. Your doctor or TED specialist may call this strabismus (struh-biz-mus).1,2
Why does strabismus happen in TED?
The retina is a layer of tissue that lines the back of the eye. The retina senses light and sends a signal to the brain so an image can be seen. We usually see a single image through 2 eyes because incoming light is directed to the same spot on the retina in each eye.2,3
Each eye has 6 attached muscles that help move the eye up, down, to the side, and at an angle. All 6 muscles work together to focus on a single object.2
Thyroid eye disease causes inflammation and hardening (fibrosis) of the muscles and tissues around the eye. This leads to swelling and thickening of the eye muscles (extraocular muscles). Muscles that are hard, thick, and swollen do not work properly, which leads to decreased eye movement. When the eyes cannot move the way they should, misalignment can occur. Misaligned eyes can cause double vision (diplopia, dip-low-pee-uh).3
Diagnosis
Eye misalignment is diagnosed by your doctor or TED specialist, usually during an eye exam. While some people have visible strabismus, others may have a more mild problem that requires additional tests. These tests include:
Cover tests
Your TED specialist uses cover tests to assess the severity of your strabismus. There are several different variations of cover tests. In 1 method, your TED specialist will cover 1 of your eyes and look at the uncovered eye to see if the movement in the uncovered eye is normal. Then your doctor will check your other eye.4,5
Corneal light reflex test (Hirschberg test)
This test is a simple and quick way your doctor can check the alignment of your eyes. Your doctor will shine a small light and ask you to focus on the light. Next, your doctor will check the reflection of the light off the surface of your eye (cornea). In those with normal eye alignment, the light reflection is even in both eyes. For those with strabismus, this reflection varies in each eye.4
Krimsky test
Like the corneal light reflex test, this test involves your TED specialist shining a small light in your eyes and asking you to focus on the light. However, with this test, prisms of different colors are placed in front of your eye. Your doctor will look for the right prism that aligns the reflection in both your eyes to determine which prism works best.4
How is strabismus treated?
If you do not have double vision, your doctor may decide to observe your symptoms as the first line of treatment. Some people with double vision due to TED may get relief by patching the affected eye. Also, special eyeglasses called prism lenses might help. These are used to bend light before it reaches the eye, allow the brain to detect a single image instead of seeing double.3,4
For some people with TED and eye misalignment, surgery to realign the eyes may be needed. Strabismus surgery should only be performed after the acute phase of TED and when eye misalignment remains stable for some time.6,7
An injection (shot) of the drug BotoxⓇ (OnabotulinumtoxinA) might be an option for some people with strabismus. This treatment blocks certain chemical signals from the nerves that cause muscle contraction. When injected into the affected muscles of the eye, Botox may help to realign the eyes.8
If you have thyroid dysfunction, such as hyperthyroidism or hypothyroidism, keeping your thyroid hormone levels within normal range might help decrease some of the symptoms related to TED. However, it is important to note that treating thyroid disorders does not directly change the course of TED. Both thyroid problems and TED require different treatments, so make sure you see your doctor to ensure you get the proper treatment.1,3
Smoking can make TED symptoms worse, especially if you have Graves’ disease. If you smoke, talk to your doctor about the best ways to quit.1,3