Thyroid Eye Disease

Original article by Tom Leach | Last updated on 7/6/2014
Printer-friendly version

Introduction

Thyroid eye disease (thyroid associated ophthalmopathy)often accompanies, and is only ever present with Grave’s disease.

  • The Mechanism is not fully understood, but it is thought to be caused by a common antigen shared by ocular and thyroid tissue. As a result, there is an immune response that causes retro-orbital inflammation.
  • There is swelling of the extra-ocular muscles which is caused by fibroblast activation. The fibroblasts are activated by cytokines which have been released by T cells and macrophages. The activation of fibroblasts causes glycosaminoglycan accumulation, which leads to oedema and fibrosis.
  • The retina is also affected.
  • The inability to fully close the eyelid may lead to corneal damage.
  • There is also conjunctival oedema and inflammation.
  • The swelling and oedema of the extra-ocular muscles leads to limitation of movement and proptosis. Proptosis is where the eye protrudes forward out of the orbit. The proptosis is usually bilateral but can be unilateral.
  • Ultimately there will be increased pressure on the optic nerve, which may cause optic atrophy.
  • Although the ocular manifestations are only related to Grave’s disease, they can occur in patients who suffer from the condition but are hypothyroid, euthyroid and hyperthyroidi.e. the severity of the eye disease is not related to the severity of the thyrotoxicosis.
  • The eye symptoms are more common after treatment with radioiodine than treatment with anti-thyroid drugs.  5-10% of cases of thyroid eye disease threaten the patients sight – however, the discomfort and cosmetic problems, as well as the risk that sight may be affected often causes patients great anxiety. Ophthalmopathy is more common in smokers.
 

Clinical features

Feature
Assessment
Frequency
Lid lag / lid retracted
Measure lid fissure width
50-60%
Grittyness, discomfort, periorbital oedema, pain, excessive tears.
Self assessment score by patient
40%
Proptosis (aka exophthalmos) this is where the eye bulges out of its socket.
Exopthalmometry or evaluation on MR/CT scan.
20%
Extraocular muscle dysfunction – typically causes diplopia (double vision) when looking up and out.
Hess chart + CT/MR to detect muscle size
10%
Corneal involvement, causing exposure keratitis
Flourescin staining
<5%
Loss of sight due to optic nerve compression
Visual acuity tests, visual field tests. CT/MR scan
<1%
In about 10% of patients, the signs will only be unilateral.
 
 
 

Treatment

  • Treatment of thyrotoxicosis will not result in improvement of symptoms of thyroid eye disease.
  • Hypothyroidism should be avoided – as this can exacerbate the problem.
  • Stopping smoking may have a large benefit – it may even alleviate the need for further treatment.
  • Eye-drops may be given to improve patient comfort and aid lubrication
  • Sleeping upright – may benefit some patients – as may taping the eyes closed
  • Systemic steroids – can reduce the inflammation if sever symptoms are present.
  • Irradiation of the orbits – can improve eye movement and reduce inflammation, but does not reduce the level of proptosis.
  • Lid surgery – will help protect the cornea if the lids cannot normally be closed
  • Surgical decompression of the orbits o   Corrective eye muscle surgery – is often very good at improving diplopia.