Eye and skin
Graves ophthalmopathy (thyroid eye disease)
Inflammation behind the eyes in thyroid disease, quieted by a short course of low-dose orbital radiation that spares the lens.
Definition
Graves ophthalmopathy (thyroid-associated orbitopathy) is an autoimmune inflammation of the orbital soft tissues — extraocular muscles and orbital fat — in patients with Graves disease. Swelling pushes the globe forward (proptosis), the eyelids retract, and the muscles become restricted, causing double vision, dry painful eyes, and in severe cases optic nerve compression. Active inflammation is usually self-limited but can leave permanent changes.
How radiation treats it
Orbital irradiation suppresses the activated lymphocytes and fibroblasts infiltrating the extraocular muscles, reducing orbital inflammation, swelling, and muscle restriction. It works in the active inflammatory phase, alongside corticosteroids, to alter the course of moderate-to-severe disease — especially diplopia and orbital congestion. It does not reverse fibrotic (late) changes such as fixed strabismus or long-standing proptosis, which require surgery.
Side effects
- Mild transient skin erythema over the lateral orbital fields.
- Temporary eye irritation or dryness during treatment.
- Cataract induction is minimized by lens-sparing half-beam technique and low total dose; the theoretical very small long-term tumor risk is weighed in young patients, and orbital RT is generally avoided when concurrent diabetic retinopathy is present.
Simulation process
The patient is positioned supine with the head immobilized and the chin slightly elevated, eyes closed and gazing straight ahead. CT simulation or a simulator image defines both orbits; the fields are angled posteriorly (usually about 5–10 degrees off the lateral orbit) so the beams spare the pituitary, brain, and sinuses. The lens and lacrimal gland are shielded or excluded with a half-beam block that stops dose at the anterior orbital rim. A custom immobilization mask or headrest ensures reproducibility.
Treatment process
A standard regimen is 20 Gy delivered in 10 daily fractions of 2 Gy over two weeks, treating both orbits with opposed lateral fields (or a single posteriorly-angled pair). Each fraction takes only a few minutes. Response typically appears weeks to a few months later as inflammation and motility improve. Patients are co-managed with endocrinology for thyroid control and ophthalmology for ocular surface care.
Key takeaways for students
- 20 Gy in 10 fractions with lens-sparing lateral half-beam technique.
- Treat active inflammation only — fibrotic changes do not respond.
- Avoid or use caution with coexisting diabetic retinopathy.