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Endocrinology

There are many endocrine conditions with important consequences for the eye and/or orbit. The most important of which to be aware of is thyroid eye disease (TED), which is outlined here.

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Background

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  • Thyroid eye disease refers to eye and orbital changes in association with abnormal thyroid function – most commonly Graves’ disease (the commonest cause of hyperthyroidism)

    • note the patient may be clinically (on examination) and biochemically (on blood tests) euthyroid, despite the presence of thyroid eye disease 

  • Circulating auto-antibodies which attack structures of the orbit and extra-ocular muscles

    • this causes inflammation of the extraocular muscles and orbital adipose tissue

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Presentation

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  • Exophthalmos (proptosis)

    • inflamed orbital tissues push the eye forwards

    • this can cause incomplete eyelid closure leading to redness, irritation / grittiness of the eye 

  • Restriction of eye movements

    • occurs due to ​grossly swollen extra-ocular muscles (especially medial and inferior recti)

  • Lid retraction and lid lag

    • Lid retraction = abnormally raised position of upper eyelid

    • Lid lag = delayed downward movement of upper lid as patient looks down

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Complications​

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  • Thyroid eye disease can cause permanent blindness, via 2 main mechanisms:

  1. Optic nerve damage (optic neuropathy)

    • occurs due to inflamed tissue in the orbit compressing the nerve behind the eye

  2. Corneal damage (keratopathy)​​

    • normally the eyelids and tear film protect the eye's surface

    • the lids cannot complete close when the eye is proptosed (pushed forwards)

    • causes causes loss of the tear film, leading to increased risk of infection, thinning, and eventual perfortation of the cornea

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Investigations

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  • Blood tests including thyroid function tests

  • MRI imaging is important: can show swelling of tissues around the eye​

  • Assessment of the optic nerve using fundal examination with the slit lamp and OCT

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Management

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  • Liaise with endocrinologists - management of thyroid disease

  • Protection of the eye's surface: lubricant eye drops and taping eye shut at night

  • Steroid therapy / immunosuppression / radiotherapy

  • Sometimes decompressive surgery is needed to release the optic nerve

  • Oculoplastic surgery may be required to improve cosmetic appearance

  • Stop smoking - smoking can worsen outcomes

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References

  • Denniston, A. K. O. and Murray, P. I. (eds) (2018) Oxford handbook of ophthalmology. 4th edn. London, England: Oxford University Press (Oxford Medical Handbooks). doi: 10.1093/med/9780198804550.001.0001.

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