Yes, thyroid eye disease (TED) can affect only one eye. While most cases involve both eyes, roughly 9 to 15% of people with TED present with symptoms in just one eye. This is called unilateral TED, and it’s well-documented in clinical literature. A cross-sectional study of 303 patients found that about 10.5% had disease limited to a single eye.
Having symptoms in only one eye can make TED harder to recognize and diagnose, since many people (and even some doctors) associate thyroid eye disease with the classic look of both eyes bulging. Understanding what unilateral TED looks like, how it’s confirmed, and whether it stays in one eye matters if you’re trying to make sense of your own symptoms.
How Common Is One-Eye Involvement?
The large majority of TED cases, around 89%, affect both eyes from the start. But the remaining 9 to 15% involve only one eye, at least initially. That’s not a tiny number. In a waiting room of ten TED patients, one or two of them would have noticeable disease on just one side.
Unilateral cases can occur across all severity levels of TED, from mild lid retraction and puffiness to more serious bulging and restricted eye movement. Having it in one eye doesn’t necessarily mean your case is milder or less serious. It simply means the inflammatory process has, for reasons that aren’t fully understood, concentrated in one orbit.
What Happens Inside the Affected Eye
TED causes changes to two main structures behind the eye: the extraocular muscles (the small muscles that move your eyeball) and the orbital fat (the cushion of fat that surrounds the eye in its socket). These tissues swell due to immune-driven inflammation, which pushes the eye forward and can restrict movement.
Research on 95 untreated patients found that muscle enlargement alone was the most common pattern, occurring in 61% of cases. Only 5% had fat expansion without muscle involvement, and 9% had both. About a quarter had no measurable increase in either. Muscle swelling tends to happen earlier in the disease, while fat expansion develops later over months to years. The fat-dominant pattern is associated with more eye bulging and longer disease duration, while muscle swelling correlates with double vision, worse eye movement, higher levels of thyroid receptor antibodies, and smoking.
In unilateral TED, these same changes occur, just on one side. A CT or MRI scan would typically show enlarged muscles or increased fat volume in one orbit while the other looks normal or near-normal.
Why Diagnosis Takes Extra Steps
When only one eye bulges or becomes inflamed, doctors can’t assume it’s thyroid-related. Several other conditions cause one-sided eye swelling, including orbital infections (cellulitis), inflammation of the eye muscles from non-thyroid causes (orbital myositis), vascular abnormalities, blood clots in the veins behind the eye, and tumors. All of these need to be ruled out before a TED diagnosis is confirmed.
Current clinical guidelines specifically recommend MRI imaging for anyone with unilateral or markedly asymmetric eye bulging. This isn’t optional. Imaging helps distinguish TED’s characteristic pattern of muscle enlargement (which spares the tendons and affects the middle and back portion of the muscle) from other conditions that can mimic it.
The diagnostic criteria work in layers. If eyelid retraction is your first symptom, confirming TED requires at least one additional finding: abnormal thyroid hormone levels or antibodies, measurable eye bulging (or a difference of more than 2 mm between the two eyes), or muscle enlargement visible on imaging. If abnormal thyroid labs came first, you need at least one eye sign like lid retraction, bulging, or muscle involvement. Having only one eye affected doesn’t change these criteria, but it does raise the bar for making sure nothing else is going on.
Anatomy plays a role in how TED presents across different populations. People of Asian descent typically show less visible swelling and eye bulging than Caucasian patients, making the signs more subtle. Shallower eye sockets and narrower spaces at the back of the orbit also increase the risk of nerve compression in these patients, which is why routine imaging is especially important.
Can It Spread to the Other Eye?
This is one of the most common concerns for people diagnosed with unilateral TED. The available evidence shows that some patients who initially present with one-eye involvement do go on to develop bilateral disease, but research hasn’t clearly pinpointed how often this happens or on what timeline. What is known is that in large studies, the proportion of patients who remain truly unilateral at the time of assessment is consistently around 10 to 15%.
If you’ve been diagnosed with TED in one eye, ongoing monitoring of the other eye through clinical exams and periodic imaging is standard practice. Controlling the underlying thyroid condition and avoiding smoking (a well-established risk factor for more severe TED) are the most actionable steps for reducing the chance of progression.
Treatment for One-Eye TED
Treatment follows the same principles whether one or both eyes are affected, but it may be applied asymmetrically. The goal is to reduce inflammation during the active phase and correct any lasting physical changes once the disease stabilizes.
Newer biologic treatments that target the underlying immune mechanism have shown significant reductions in eye bulging, inflammation scores, and double vision in both orbits when both are affected. For unilateral cases, the treatment still targets the systemic immune process driving the disease, even though symptoms are visible on only one side.
When surgery is needed, it can be performed on just one orbit. Orbital decompression, which removes bone or fat to create more space and reduce bulging, is commonly done on individual eyes. In one review of 55 patients (93 orbits total), lateral wall decompression reduced eye bulging by an average of 4.2 mm. More extensive procedures achieved reductions up to 7.6 mm on average. The most common side effects were temporary numbness around the eye (affecting about 29% of patients after lateral wall surgery) and new double vision afterward (about 9% for lateral wall, higher for more aggressive approaches). These outcomes apply per orbit, so surgery on one eye carries these risks for that eye alone.
For people whose main concern is cosmetic asymmetry, where one eye looks noticeably different from the other, single-eye decompression can help restore a more balanced appearance. Eyelid surgery and eye muscle surgery can also be performed on one side to address retraction or misalignment.