Exophthalmos: Causes, Symptoms and Treatment
Exophthalmos describes the abnormal protrusion of one or both eyeballs from the eye socket. The most common cause is Graves disease, a thyroid disorder.
Things worth knowing about "Exophthalmos"
Exophthalmos describes the abnormal protrusion of one or both eyeballs from the eye socket. The most common cause is Graves disease, a thyroid disorder.
What is Exophthalmos?
Exophthalmos (also spelled exophthalmus, or referred to as proptosis or protrusio bulbi) is the abnormal forward displacement of the eyeball (bulbus oculi) beyond the bony orbit. The condition may affect one eye (unilateral) or both eyes (bilateral) and is most often a sign of an underlying medical condition. A protrusion of more than 20 mm, or a side-to-side difference of more than 2 mm, is generally considered clinically significant.
Causes
The most common cause of bilateral exophthalmos is thyroid eye disease (also called Graves orbitopathy or endocrine orbitopathy), an autoimmune condition closely associated with Graves disease (hyperthyroidism). In this condition, autoantibodies attack the connective tissue and eye muscles within the orbit, causing swelling and forward displacement of the eyeball.
Other possible causes include:
- Orbital tumors (e.g., hemangioma, lymphoma, metastases)
- Orbital inflammation (orbital pseudotumor, orbital cellulitis)
- Vascular abnormalities such as cavernous sinus fistula or orbital hematoma
- Bone disorders affecting the orbit (e.g., Paget disease, fibrous dysplasia)
- Rarely: systemic diseases such as lymphoma or leukemia
Symptoms
In addition to the visible protrusion of the eye, affected individuals may experience:
- Foreign body sensation, burning, or excessive tearing
- Light sensitivity (photophobia)
- Double vision (diplopia) due to involvement of the extraocular muscles
- Incomplete eyelid closure (lagophthalmos), which can lead to corneal dryness and damage
- Pressure or pain behind the eyes
- In severe cases: visual impairment or even vision loss due to compression of the optic nerve
Diagnosis
Diagnosis is based on a combination of clinical examination and imaging:
- Hertel exophthalmometry: measurement of the degree of eyeball protrusion using a dedicated instrument
- Ophthalmological assessment: visual acuity, intraocular pressure, slit-lamp examination, visual field testing
- Imaging: computed tomography (CT) or magnetic resonance imaging (MRI) of the orbit to evaluate soft tissues, extraocular muscles, and the optic nerve
- Laboratory tests: thyroid function tests (TSH, fT3, fT4) and TSH receptor antibodies (TRAb) if thyroid eye disease is suspected
Treatment
Treatment depends on the underlying cause and severity of the condition:
Conservative Measures
- Lubricating eye drops and gels to protect the cornea from dryness
- Sunglasses to protect against light and wind exposure
- Smoking cessation (smoking significantly worsens thyroid eye disease)
Medical Therapy
- Corticosteroids (e.g., intravenous methylprednisolone) to reduce inflammation in active thyroid eye disease
- Teprotumumab: a monoclonal antibody specifically approved for the treatment of Graves orbitopathy
- Treatment of the underlying thyroid dysfunction with antithyroid drugs, radioiodine therapy, or surgery
Radiation Therapy
Low-dose orbital radiotherapy may be used in active, inflammatory thyroid eye disease to suppress the inflammatory response.
Surgical Treatment
- Orbital decompression: surgical enlargement of the bony orbit to relieve pressure on the optic nerve and eye muscles
- Strabismus surgery for persistent double vision
- Eyelid surgery to correct incomplete eyelid closure
References
- Wiersinga WM, Kahaly GJ (eds.): Graves' Orbitopathy: A Multidisciplinary Approach. Karger Publishers, 3rd edition, 2017.
- Bartalena L et al.: The 2021 European Group on Graves' Orbitopathy (EUGOGO) clinical practice guidelines for the medical management of Graves' orbitopathy. European Journal of Endocrinology, 2021. DOI: 10.1530/EJE-21-0479.
- Dolman PJ: Evaluating and managing the patient with Graves orbitopathy. Medical Clinics of North America, 2015. DOI: 10.1016/j.mcna.2015.01.003.
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