Thyroid eye disease

12/08/2014 by admin | Ophthalmology

Definition: is an organ-specific idiopathic auto-immune disease. It is characterised by an active inflammatory orbital phase lasting months to years, followed by an ‘inactive’ fibrotic phase.It can be sight-threatening as acute progressive disease affects the optic nerve and cornea. Most patients with thyroid eye disease (TED) have clinical and/or biochemical evidence of hyper/hypothyroidism but some are euthyroid (at least at the time of presentation).

Classification / type of disease:

Epidemiology:

  • The incidence of TED is 3-16 cases/100,000/year.
  • The ophthalmic complications of Graves’ disease or thyrotoxicosis affects between 25% and 50% of those with the disease.
  • F:M (4:1).
  • The usual age of onset is between 30 and 50.
  • TED can be more severe in men over the age of 60.

 

Presenting symptoms / signs:concurrent thyrotoxicosis, Ocular irritation, Ache (worse in the mornings) behind the eye, Red eyes, Cosmetic changes, Diplopia (restricted ocular mobility, initially involving the inferior rectus muscles). Gradually, proptosis (exophthalmos) may develop accompanied by: Lid retraction and lid lag, Conjunctival injection and chemosis (oedema), Orbital fat prolapse, Exposure keratopathy (photophobia, tearing, grittiness, pain) due to incomplete lid closure, strabsimus in elderly. Also look out for systemic dysthryroid symptoms.

 

Diagnostic investigations: 

  • TSH and free thyroxine (FT4).
  • Thyroid auto-antibodies: anti-TSH receptor, anti-thyroid peroxidase and anti-thyroglobulin antibodies (although these have poor sensitivity and specificity).
  • CT or preferably MRI of orbits. MRI is better at showing soft tissue; CT will be helpful if surgery for orbital decompression is planned. There will be enlarged extra-ocular muscles (with tendon sparing) ± an increase in orbital fibro-adipose tissue.
  • Thyroid uptake scan or orbital biopsy are sometimes required.

 

Aetiology:

  • Smoking (x 7-8)
  • Female sex
  • Middle age
  • HLA-DR3, HLA-B8 and the genes for CTLA4 and the TSH receptor
  • Auto-immune thyroid disease
  • Uncontrolled thyroid dysfunction
  • Radio-iodine therapy linked to progressive Graves ophthalmopathy

Pathophysiology:

Transmission

Treatment / management:  

  • Medical treatment

  • Immunosuppression is the mainstay of treatment in active disease. This is often systemic corticosteroids (in sight-threatening eye disease, high dose intravenous treatment may be needed) but ciclosporin, methotrexate and azathioprine may all be used.
  • Radiotherapy

  • Surgical treatment = Inferior orbital decompression surgery

  • Future therapies:Rituximab, anti-oxidant, anti-TNF-α drugs (enteracept), somatostatin analogues and intravenous immune globulin.

Complications

  • Corneal exposure
  • Strabismus
  • Pressure on the optic nerve
  • Poor cosmetic result

Differentials: allergic conjunctivitis, dry eye, Orbital myositis, Chronic progressive external ophthalmoplegia, Idiopathic orbital inflammatory disease, Lymphoproliferative disorders, Caroticocavernous fistula, Myasthenia gravis (in elderly males with inactive disease), Cushing’s syndrome, obesity

Prognosis:

Mild disease: often self-limiting and resolves spontaneously over 1-5 years

Severe disease: good long-term outcome is dependent on timely intervention in the acute phase with attention to avoiding sight-threatening complications. Poor prognostic factors include:

  • Older age at onset
  • Rapid progression at onset
  • Longer duration of active disease
  • Drop in visual acuity during active phase
  • Male gender
  • Smoker
  • Diabetes

 

Terminology: Proptosis = exopthalmous

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