Treating Diplopia in the Chronic Phase of Thyroid Eye Disease

Thyroid Eye Disease can often cause noticeable changes such as eye bulging (proptosis), eyelid retraction, redness, swelling, and double vision (diplopia). Double vision, or diplopia, is one of the most challenging long-term complications of thyroid eye disease (TED). TED progresses through an active inflammatory phase and a chronic inactive phase. While many patients experience diplopia during the active phase of the disease, some continue to struggle with persistent double vision long after the inflammation has subsided (2). This chronic phase can significantly affect daily life, making activities such as driving, reading, working on a computer, and navigating stairs difficult or even unsafe.

Fortunately, persistent double vision is not a permanent disability that patients must live with. Although treatment strategies adopted for the chronic phase differ from those used during the active stage of TED, several highly effective options are available (3). The key is understanding why double vision persists in the chronic phase and selecting the treatment that best targets the underlying cause.

Why Does Diplopia Persist After Thyroid Eye Disease Becomes Inactive?

TED progresses through two broad stages: an active inflammatory phase followed by an inactive, or chronic, phase (4). During the active phase, inflammation arising from the autoimmune attack causes swelling of the extraocular muscles and orbital tissues. As the disease gradually dissipates, inflammation concomitantly decreases, but the tissues often do not completely revert to normal.

Instead, the enlarged eye muscles may develop fibrosis, or scar tissue. Fibrotic muscles lose flexibility and can no longer move the eyes normally. Rather than active inflammation causing misalignment of the eyes, the problem becomes a mechanical restriction of eye movement. As a result, the eyes no longer focus in the same direction, causing the brain to receive two separate images, a condition known as binocular diplopia (2). This restrictive form of double vision is one of the hallmarks of chronic TED.

Unlike active disease, where combating inflammation may restore eye movement, chronic diplopia typically requires treatments that address the underlying structural consequences of the disease. Before any definitive treatment course is decided, physicians must first determine whether TED has stabilized. This distinction is extremely important because operating on eye muscles while inflammation is still active may lead to unpredictable results, as eye alignment can continue to change. Most specialists recommend waiting until the disease has remained stable for several months before proceeding with corrective surgery. Stability is assessed by monitoring symptoms such as eye alignment, proptosis measurements, and the Clinical Activity Score (CAS). Imaging studies such as CT or MRI may also help evaluate muscle enlargement and confirm that active inflammation has largely resolved.

Prism Glasses: A Non-Surgical Option

For patients with mild or moderate stable diplopia, prism glasses are often the first line of treatment (5). Prisms are special lenses incorporated into eyeglasses that bend the incoming light, helping realign the two separate images from either eye, allowing the brain to merge them into a single image. They do not rectify the underlying muscle defects but can significantly improve vision for daily function. Prisms work best when the double vision is relatively small in magnitude, and eye alignment is stable.

Temporary press-on plastic prisms, Fresnel prisms, can be applied to existing eyeglasses to test prescriptions or accommodate minor alignment shifts before committing to permanent lenses.

Although prism glasses can be highly effective, they are less helpful for patients whose double vision varies dramatically depending on the direction of gaze or in patients whose eye deviation is too large to be corrected with prisms alone.

Strabismus Surgery: The Gold Standard for Chronic Diplopia

When prism glasses no longer provide adequate relief, strabismus surgery is often considered the most effective treatment for chronic diplopia caused by TED (6).

Unlike pediatric strabismus surgery, which treats childhood strabismus, surgery for TED-related strabismus focuses on correcting the restrictive effects of fibrotic muscles. Rather than strengthening the weakened muscles, surgeons usually recess the tight, fibrotic muscles, allowing the eyes to regain better alignment. These often include the inferior rectus muscle, which controls downward movement, and the medial rectus muscle, which moves the eye inward, and are among the muscles most commonly affected by TED.\

The primary goal of surgery is to maximize the zone of comfortable single vision directly ahead and when reading, rather than achieving perfect alignment in every extreme gaze direction.

Why Orbital Decompression Comes First

Some patients with TED might require more than one surgical procedure. When significant eye bulging (proptosis) is present, orbital decompression surgery is typically performed before strabismus surgery. This sequence is important because orbital decompression changes the position of the eye within the orbit (7). Performing eye muscle surgery first could result in new misalignment after decompression, making the original correction inaccurate. For this reason, rehabilitation usually follows a staged approach with:

• Orbital decompression (if needed to treat proptosis or optic nerve compression )
• Strabismus surgery (to correct muscle tightness and double vision)
• Eyelid surgery (to address retraction or asymmetry)

This sequence provides the greatest chance of achieving stable, predictable long-term results.

Medical Therapy

Once TED has entered the chronic, inactive phase, medications become far less effective in treating persistent diplopia. Steroids and other anti-inflammatory medications primarily target active inflammation. If scar tissue has already formed within the extraocular muscles, reducing inflammation alone cannot restore normal muscle flexibility.

Newer biologic therapies, such as teprotumumab (Tepezza), have demonstrated impressive improvements in diplopia when used during active disease. However, their role in patients with fully inactive, fibrotic disease is more limited, as the primary problem is no longer inflammation but permanent structural remodeling. Therefore, surgical rehabilitation remains the standard treatment for many patients with chronic restrictive diplopia.

Setting Realistic Expectations

One of the most important aspects of treating chronic diplopia is setting appropriate expectations since the goal is functional vision rather than perfection. Most patients experience substantial improvements in straight-ahead vision and reading, allowing them to resume normal day-to-day activities, such as driving, working, and social interactions, with much greater confidence.

However, because TED causes complex muscle restrictions, complete elimination of double vision in every direction of gaze is not always possible. Patients may continue to notice diplopia when looking upward, downward, or to the sides. Experienced surgeons always discuss these expectations before surgery, so patients understand the likely benefits and limitations.

Lifestyle Adjustments During Recovery

While awaiting definitive treatment or recovering from surgery, several strategies can help reduce the impact of chronic diplopia. Some patients benefit from temporarily covering one eye during particularly challenging tasks. Others find that adjusting computer monitor height, increasing lighting, or taking frequent visual breaks reduces eye strain. Maintaining stable thyroid hormone levels and avoiding smoking are also important, as thyroid fluctuations and smoking are associated with poorer overall outcomes in TED. Regular follow-ups with both an endocrinologist and an ophthalmologist experienced in TED ensure that any recurrence of inflammation or changes in alignment are detected early.

The Bottom Line

Persistent double vision during the chronic phase of TED can be frustrating, but it is often highly treatable. Once inflammation has resolved and eye alignment has stabilized, treatment shifts from controlling the autoimmune process to correcting the structural changes left behind. Depending on the severity of the misalignment, options such as prism glasses, staged orbital rehabilitation, and strabismus surgery can restore comfortable single vision for many patients and significantly improve quality of life. The most successful outcomes come from careful timing and individualized care.

Working with a multidisciplinary team experienced in TED diplopia management ensures optimal treatment. If you are interested in learning more about treatment options for diplopia in TED, do not hesitate to schedule an appointment with Dr. Raymond Douglas.

References

1. Shah, S. S. & Patel, B. C. in StatPearls     (2025).
2. Johnson, B. T., Jameyfield, E. & Aakalu, V. K. Optic neuropathy and diplopia from thyroid eye disease: update on pathophysiology and treatment. Curr Opin Neurol 34, 116-121 (2021). https://doi.org/10.1097/WCO.0000000000000894
3. Fox, T., Kossler, A. L. & Dosiou, C. Thyroid Eye Disease: Management, Advances, and Future Opportunities. Endocr Pract 31, 1319-1328 (2025). https://doi.org/10.1016/j.eprac.2025.06.011
4. Barman Kakil, S. & Arslan, N. Evaluation of clinical and ocular surface changes in thyroid eye disease: impact of treatment and risk factors. Ther Adv Ophthalmol 17, 25158414251393119 (2025). https://doi.org/10.1177/25158414251393119
5. Gunton, K. B. & Brown, A. Prism use in adult diplopia. Curr Opin Ophthalmol 23, 400-404 (2012). https://doi.org/10.1097/ICU.0b013e3283567276
6. Akbari, M. R., Mirmohammadsadeghi, A., Mahmoudzadeh, R. & Veisi, A. Management of Thyroid Eye Disease-Related Strabismus. J Curr Ophthalmol 32, 1-13 (2020). https://doi.org/10.1016/j.joco.2019.10.002
7. Kauh, C. Y. et al. Compressive Optic Neuropathy and Repeat Orbital Decompression: A Case Series. Ophthalmic Plast Reconstr Surg 31, 385-390 (2015). https://doi.org/10.1097/IOP.0000000000000356
8. Volpe, N. J., Mirza-George, N. & Binenbaum, G. Surgical management of vertical ocular misalignment in thyroid eye disease using an adjustable suture technique. J AAPOS 16, 518-522 (2012). https://doi.org/10.1016/j.jaapos.2012.08.010