Makindo Medical Notes

Introduction

Thyroid eye disease (TED), also known as Graves' orbitopathy or Graves' ophthalmopathy, is an autoimmune disorder commonly associated with Graves' disease, a type of hyperthyroidism. TED involves inflammation and swelling of the extraocular muscles, orbital fat, and connective tissue. This condition can result in a range of eye symptoms, including proptosis (bulging eyes), diplopia (double vision), lid retraction, and in severe cases, vision loss. TED primarily affects adults but can occur at any age, and it often presents concurrently with thyroid dysfunction.

Pathophysiology

• TED is an autoimmune process in which antibodies mistakenly target the thyroid and the orbital tissue. In particular, the thyrotropin receptor antibodies (TRAbs) found in Graves’ disease stimulate the release of cytokines and other immune mediators in the orbit.
• These stimulate fibroblasts to produce glycosaminoglycans, leading to inflammation, edema, and enlargement of the extraocular muscles and orbital fat. The resulting changes lead to the clinical manifestations of TED, including:
  • Inflammation of the extraocular muscles, leading to restricted eye movement and diplopia.
  • Proptosis, caused by the expansion of orbital fat and muscles, pushing the eyeballs forward.
  • Eyelid retraction, due to inflammation of the levator muscles.
  • Corneal exposure, which can lead to dryness and ulceration.
  • Optic neuropathy, in severe cases, due to compression of the optic nerve at the orbital apex.

Risk Factors

• Graves' Disease: Most commonly associated with TED (occurs in 25-50% of Graves' patients).
• Smoking: Strongly correlated with increased severity and poorer response to treatment.
• Female Gender: Women are more commonly affected, though men may experience more severe forms of the disease.
• Hyperthyroidism and Hypothyroidism: TED can occur in patients with any thyroid status (hyper-, hypo-, or euthyroid).
• Radioactive Iodine Therapy (RAI): While effective for treating hyperthyroidism, RAI can worsen TED in some cases.

Clinical Presentation

TED presents with a spectrum of symptoms, varying from mild to severe. Early recognition is crucial to manage the disease effectively and prevent complications.

• Early Symptoms
  • Grittiness or irritation in the eyes.
  • Excessive tearing.
  • Photophobia (sensitivity to light).
  • Periorbital edema (swelling around the eyes).
  • Redness in the conjunctiva.
  • Mild proptosis (eye bulging).
  • Eyelid retraction, giving a “staring” appearance.
• Moderate to Severe Symptoms
  • More noticeable and asymmetric proptosis.
  • Diplopia (double vision) due to restricted movement of inflamed extraocular muscles.
  • Severe lid retraction causing corneal exposure.
  • Corneal ulceration due to exposure keratopathy.
  • Compressive optic neuropathy leading to decreased visual acuity, colour vision, or visual field defects.

Diagnosis

Clinical evaluation remains the cornerstone of diagnosis. Key clinical findings include proptosis, lid retraction, and restricted eye movements. The following assessments help confirm and classify TED:

Comprehensive Eye Examination

• Visual acuity: Regular monitoring of vision is critical, especially in severe cases to detect optic neuropathy.
• Pupil examination: Look for signs of relative afferent pupillary defect (RAPD) in cases of optic nerve compression.
• Exophthalmometry: Used to measure proptosis (normal range: 12-21mm).
• Eye movement testing: To identify muscle restriction or paresis.

Tests

• CT Scan or MRI of the orbits: Helps assess the enlargement of extraocular muscles and detect optic nerve compression.
• Ultrasound: Can be used as a quick bedside tool to measure muscle thickness and proptosis.
• Thyroid Function Tests (TFTs): TSH, Free T4, T3 to correlate with systemic thyroid disease.
• Thyrotropin receptor antibodies (TRAbs) and anti-thyroid peroxidase (TPO) antibodies can help confirm autoimmune thyroid disease.
• Visual Field Testing : Important in detecting early optic nerve compression or neuropathy.

Management

• The management of TED requires a multidisciplinary approach, involving endocrinologists, ophthalmologists, and sometimes surgeons. The goals are to control the underlying thyroid disease, reduce inflammation, and address the eye complications. Treatment can be divided into three phases: active, quiescent, and rehabilitative.
• Active Phase (Inflammatory Phase): This phase involves the acute inflammation and can last 6 months to 2 years. Early intervention is key to preventing long-term complications.
  • Control Thyroid Function: Euthyroid status is essential for optimal TED management. Thyroid function should be tightly controlled using antithyroid medications, radioactive iodine (RAI), or surgery (thyroidectomy).
  • Corticosteroids: High-dose corticosteroids (oral or IV) can reduce inflammation and improve symptoms, especially in moderate to severe cases.
  • Smoking Cessation: Smoking is strongly associated with TED worsening. Patients should be encouraged and supported to quit smoking. Orbital Radiotherapy: In moderate-to-severe cases, orbital radiotherapy can be used to reduce inflammation in combination with corticosteroids.
• Quiescent Phase: This phase occurs once the inflammation has subsided. Treatment focuses on managing residual symptoms like diplopia and proptosis.
  • Prism Glasses: Can help reduce double vision in patients with residual muscle imbalance. Orbital Decompression
  • Surgery: Indicated for patients with severe proptosis or optic nerve compression. This surgery involves removing bone from the orbit to create more space for the swollen tissues.
• Rehabilitative Phase: his phase focuses on correcting the residual effects of the disease, such as persistent proptosis, lid retraction, and eye misalignment.
  • Eyelid Surgery: Can correct severe lid retraction and improve both function and cosmetic appearance.
  • Strabismus Surgery: For patients with significant eye misalignment or persistent diplopia, strabismus surgery can correct eye muscle imbalance.

Conclusion

Thyroid eye disease is a complex condition requiring a multidisciplinary approach. Early recognition and management are crucial to minimize long-term complications such as vision loss. Controlling thyroid function, reducing inflammation, and addressing eye-specific symptoms through a combination of medical, surgical, and rehabilitative treatments can significantly improve outcomes for patients.