The symptoms of thyroid eye disease (TED) can be distressing, as they may cause noticeable changes to your appearance and affect your eyesight. The symptoms of TED are different for everyone and range from mild to severe. Recognizing the symptoms of TED early is crucial to help prevent more serious complications. The more you learn about TED, the better you can track any changes in your vision, which helps you communicate clearly with your doctors.

What Causes Thyroid Eye Disease Symptoms?

TED is caused by an autoimmune disorder — a condition when your immune system mistakenly attacks your healthy tissue. When you have TED, your immune system attacks the tissue and muscles around your eyes, causing inflammation. This inflammation causes the symptoms of TED.

TED is associated with Graves’ disease — a type of autoimmune disease that can result in high levels of thyroid hormones (hyperthyroidism). About half of people with Graves’ disease develop TED. However, TED can also affect people with normal thyroid hormone levels or hypothyroidism (low thyroid hormone levels).

How Long Do Thyroid Eye Disease Symptoms Last?

Symptoms of TED often begin within six months of being diagnosed with Graves’ disease. However, they can also start before you’re diagnosed or after you’ve been treated for Graves’ disease. TED symptoms can be severe even if your thyroid disease isn’t.

TED has an active phase and an inactive phase. During the active phase, inflammation and swelling cause TED symptoms. The active phase can last from six months to about two years. After the active phase, TED stops getting worse, and the inactive phase starts. Although some symptoms may improve after the active phase, others can remain if they aren’t treated.

TED symptoms usually involve both eyes, but you may notice TED symptoms in one eye more than the other. Continue reading to learn more about the seven symptoms of TED.

1. Bulging Eyes

Bulging of the eyes is often the most noticeable symptom of TED. If you have bulging eyes, you may look like you’re constantly startled or staring. The medical term for bulging eyes is proptosis or exophthalmos. Bulging eyes is common in people with TED. About 1 in 3 people with hyperthyroidism caused by Graves’ disease develop bulging eyes.

The two main reasons TED causes bulging eyes are inflammation in the tissues behind your eye and in the muscles controlling your eyelids.

Inflammation in the fat tissue and muscles behind your eyes can cause fluid to build up. This condition can push your eyes forward, making them appear more noticeable.

Additionally, inflammation can cause scarring in the muscles that control your eyelids. When muscles develop scar tissue, they may become shorter and less flexible. These shorter eyelid muscles can result in eyelid retraction (when your eyelids are pulled back). Eyelid retraction can make the look of bulging eyes more pronounced.

Bulging of the eyes may not improve after the active phase of the disease. However, surgery and other treatments can help the eyes look more normal.

2. Swelling

Many people with TED develop swelling around their eyes. Swelling can happen when fluid builds up in the fat surrounding your eyes.

Swelling around your eyes may look like bags under your eyes or puffy eyelids. These changes around your eyes can make some people feel like they look older than they are.

If the swelling doesn’t go away, surgery can help remove some of the swelling and improve the appearance of your eye area.

3. Double Vision

Double vision — also known as diplopia — causes you to see two images of a single object. It can happen if inflammation caused by TED damages the muscles that control your eye movement. As your eye muscles heal, they can become larger and less flexible. This can make your eyes not line up correctly. When one eye turns in a different direction than the other, it’s called strabismus.

Some people with TED have double vision all the time. Others may only notice it when they’re looking in a certain direction. The amount of double vision you have may change over time.

Double vision may not get better in the inactive phase of TED. You may need to wear special glasses called prisms or have surgery to correct double vision.

4. Dry, Irritated Eyes

Bulging eyes and eyelid retraction can make it difficult for your eyelids to close. If you have trouble closing your eyelids all the way, especially at night while you sleep, your cornea (the outermost clear layer of your eye) can become dried out.

Dry eyes can feel very uncomfortable. You might feel like you constantly have something in your eye. It can also feel like your eyes are gritty, stinging, or burning. You might also notice that your eyes look red or you have mucus coming out of your eyes.

A potentially serious consequence of dry eyes is a sore on your cornea called a corneal ulcer. A corneal ulcer can cause pain and redness and even cause you to lose your vision.

5. Watery Eyes

Your eyes can become watery if your eyes make more tears than usual, causing your tears to roll down your face. You may wonder, “If TED causes dry eyes, how does it also cause watery eyes?” However, it’s common for the two symptoms to go hand in hand.

You may make more tears than usual if the glands in your eye also don’t make enough oils. These oils help your tears form a film on your eyes to prevent drying. Without these oils, your tears evaporate too quickly. When your tears evaporate too quickly, your tear glands produce more tears. But these extra tears don’t work well to prevent dry eyes without the right oils.

6. Sensitivity to Light

Most people with dry eyes also experience light sensitivity, called photophobia. This is also true for people with dry eyes caused by TED. If you have light sensitivity, you may notice that you’re frequently squinting or blinking, shielding your eyes from light, or prefer dimmer lights to bright lights.

Dry eyes can cause light sensitivity caused by scratches or irritation on your cornea. Additionally, the nerves that send pain signals in your eyes can become more sensitive in people with dry eyes. This extra sensitivity may cause an abnormal reaction to bright lights.

7. Vision Loss

Vision loss is a potentially serious symptom of TED. There are two main ways that TED can cause vision loss.

The first way that TED can cause vision loss is from damage to your cornea. If you can’t close your eyelids because of eyelid retraction and bulging eyes, you may develop corneal ulcers that can cause scarring and damage your vision.

The second way TED causes vision loss is by putting pressure on your optic nerve — the main nerve that runs from your eye to your brain. In rare cases, inflammation can cause your eye muscles to enlarge so much that they press on your optic nerve. When your optic nerve is compressed, it can cause vision loss. One study found that almost 10 percent of people with TED had optic nerve compression.

If you notice any changes in your vision, it’s important to see your health care provider as soon as possible. Catching issues early can help prevent more serious problems and protect your eyesight. Your doctor can provide treatments that may improve your vision and ensure you continue to enjoy good eye health.

Talk With Others Who Understand

On TEDhealthteam, the social network for people living with thyroid eye disease and their loved ones, members ask questions, give advice, and share their stories with those who understand life with TED.

What TED symptoms have you noticed? Share your experience in the comments below, or start a conversation by posting on your Activities page.