Thyroid Eye Disease (Graves’ Ophthalmopathy)
Ophthalmology: Autoimmune Orbital Inflammation
1. Pathophysiology
TED is an autoimmune process where T-cells target the TSH receptors on orbital fibroblasts. This leads to the activation of fibroblasts, production of glycosaminoglycans (hyaluronic acid), orbital fat expansion, and extraocular muscle enlargement (edema and fibrosis).
2. Clinical Manifestations
| Sign/Symptom | Clinical Characteristic |
|---|---|
| Lid Retraction | The most common early sign exposes the sclera. |
| Exophthalmos | Proptosis due to increased orbital volume. |
| Restrictive Myopathy | “I‘M SLOW”: Inferior rectus is most commonly involved, limiting upward gaze. |
| Optic Neuropathy | Rare but serious; caused by muscle compression at the orbital apex. |
3. NEET High-Yield Pearls
- Muscle Involvement Mnemonic: **I**ndian **M**edical **S**chool **L**ibrary: Inferior > Medial > Superior > Lateral rectus.
- Risk Factor: Smoking is the single most significant modifiable risk factor for the progression and severity of TED.
- Diagnosis: Usually clinical; MRI or CT orbits will show “muscle belly enlargement” while sparing the tendons (key differentiator from orbital pseudotumor).
- Treatment: Control thyroid status first; use lubricating drops, steroids for the active phase, radiation for specific cases, and surgical decompression (if sight-threatening or for rehabilitative purposes).