Proptosis

Forward displacement of the globe. Exophthalmos is the term used for thyroid related protrusion; proptosis covers any cause.

• Normal exophthalmometer reading is 12 to 21 mm in white adults (upper limit about 23 to 24 mm in people of African descent, 18 to 20 mm in East Asian adults). An interocular asymmetry above 2 mm or a rise of 2 mm or more from baseline is abnormal.
• Pseudoproptosis: contralateral enophthalmos, ipsilateral lid retraction, high axial myopia, large globe (buphthalmos), shallow orbits (craniosynostosis), facial asymmetry.
• Causes by pattern and age:
  • Unilateral adult: thyroid eye disease (most common cause overall), idiopathic orbital inflammation, lymphoproliferative disease, cavernous haemangioma, lacrimal gland tumour, meningioma, metastasis, carotid cavernous fistula, mucocele, orbital cellulitis.
  • Bilateral adult: thyroid eye disease, lymphoma, IgG4-related disease, granulomatosis with polyangiitis, sarcoidosis, cavernous sinus thrombosis.
  • Children: orbital cellulitis, capillary haemangioma, lymphangioma, rhabdomyosarcoma, dermoid cyst, leukaemia (chloroma), metastatic neuroblastoma, optic nerve glioma, Langerhans cell histiocytosis, plexiform neurofibroma.
  • Intermittent: orbital varix (increases with Valsalva or head down position), recurrent orbital haemorrhage.
  • Pulsatile: carotid cavernous fistula (with bruit), neurofibromatosis type 1 with sphenoid wing dysplasia, absent orbital roof.

• Direction of displacement: axial (retrobulbar muscle cone mass, thyroid, optic nerve tumour), downward and outward (frontal sinus mucocele, frontoethmoidal), upward (maxillary or inferior orbital mass), inferomedial (lacrimal gland), lateral (ethmoidal mass).
• Tempo: days (infection, haemorrhage, carotid cavernous fistula, rhabdomyosarcoma), weeks to months (inflammation, lymphoma, metastasis), years (cavernous haemangioma, meningioma, dermoid, benign tumours).
• Pain suggests inflammation, infection, perineural spread or acute haemorrhage; painless indicates benign tumour or thyroid disease.
• Features of compromise: reduced acuity and colour vision, relative afferent pupillary defect, disc swelling or atrophy, choroidal folds, raised intraocular pressure, restricted motility with diplopia, lid retraction (thyroid), ptosis (apical lesions), exposure keratopathy.
• Palpable mass, periorbital oedema, conjunctival chemosis, bruit, pulsation, venous engorgement (dilated corkscrew episcleral vessels in fistulas).

• Exophthalmometry (same instrument and base measurement each visit), retropulsion, forced duction, visual fields, colour vision, pupils, fundus, intraocular pressure in primary and upgaze, palpation, auscultation for bruit, systemic examination (thyroid, lymph nodes, skin, sinuses, breast, lung, prostate).
• CT orbits with contrast (bone, calcification, sinus disease, fracture, muscle enlargement) and MRI with fat suppression and contrast (soft tissue, optic nerve, intracranial extension); ultrasound for cystic, vascular and muscle lesions.
• Blood tests: thyroid function and TSH-receptor antibodies, full count, ESR and CRP, ANCA, ACE, IgG4, serum protein electrophoresis, LDH, blood cultures if infection.
• Tissue diagnosis when tumour or inflammatory disease is suspected: incisional or excisional biopsy with fresh tissue for flow cytometry (lymphoma). Fine needle aspiration is used for metastasis and cystic lesions with care.
• Angiography (CT or MR angiography, catheter angiography) for suspected vascular lesion.

• Directed by cause: antibiotics and drainage for infection; steroids and immunosuppression for inflammation; radiotherapy and chemotherapy for malignancy; endovascular closure for carotid cavernous fistula; surgical removal of benign encapsulated tumours.
• Protect the cornea: preservative free lubricants every 2 to 4 hours, ointment at night, taping or tarsorrhaphy, moisture chamber, treat exposure keratopathy early.
• Urgent decompression (lateral canthotomy and cantholysis, bony decompression) when there is an acute compressive optic neuropathy or tense orbit.
• Optic nerve monitoring: acuity, colour, pupils, fields and disc each visit; prompt escalation when function falls.
• Refer orbital mass of unknown cause for biopsy and multidisciplinary care.