Chemosis

Chemosis is oedema of the bulbar conjunctiva caused by fluid accumulation in the loose subconjunctival connective tissue, which can balloon over the limbus and lid margin.

• Causes:
  • Allergic and inflammatory: allergic conjunctivitis, angioedema, anaphylaxis, contact dermatitis.
  • Infective: adenoviral and gonococcal conjunctivitis, orbital and preseptal cellulitis, dacryoadenitis.
  • Orbital venous congestion: thyroid eye disease, carotid cavernous fistula, cavernous sinus thrombosis, orbital tumour, superior vena cava obstruction.
  • Lymphatic obstruction or hypoalbuminaemia: nephrotic syndrome, cardiac failure, myxoedema.
  • Post-surgical or traumatic: after eyelid or orbital surgery, blepharoplasty, retinal detachment surgery, lagophthalmos or exposure.
  • Others: conjunctival lymphangiectasia, ovarian hyperstimulation, snake venom.
• It is a sign, not a diagnosis, and management is directed at the cause.

• Translucent, gelatinous swelling of the conjunctiva, which may prolapse between the lids or obscure the cornea, with difficulty closing the eye.
• Foreign body sensation, watering, blurred vision, and exposure keratopathy if lids cannot close.
• Associated features point to cause:
  • Itching, bilateral and stringy discharge: allergy.
  • Purulent discharge and preauricular node: infection.
  • Proptosis, retraction, restricted motility, congested vessels: thyroid eye disease or orbital disease.
  • Pulsatile proptosis, bruit, dilated corkscrew episcleral vessels: carotid cavernous fistula.
  • Fever, painful ophthalmoplegia, bilateral involvement: cavernous sinus thrombosis.
  • Generalised oedema or facial swelling: angioedema, renal and cardiac disease.

• Detailed history (onset, itching, trauma, surgery, medication, systemic symptoms) and examination, including proptosis (exophthalmometry), motility, pupils, lid closure, intraocular pressure, optic nerve function and fundus.
• Investigations by suspected cause: FBC, CRP, thyroid function and antibodies, serum albumin, renal function and urinalysis, conjunctival swabs, CT or MRI orbits with contrast (and venography), carotid duplex or angiography for fistula, serum tryptase if anaphylaxis suspected.
• Slit lamp for exposure keratopathy.

• Treat the underlying cause:
  • Allergy: remove allergen, cold compresses, olopatadine 0.1 percent twice daily, oral antihistamine (cetirizine 10 mg daily); anaphylaxis: adrenaline 0.5 mg (0.5 mL of 1 in 1000) intramuscularly into the lateral thigh, repeat after 5 minutes if needed; hydrocortisone 200 mg intravenously; chlorphenamine 10 mg intravenously.
  • Infection: appropriate antibiotics or antivirals; orbital cellulitis requires intravenous ceftriaxone 2 g daily with metronidazole 500 mg every 8 hours.
  • Thyroid eye disease: lubricants, head elevation, and immunosuppression for active disease.
  • Cardiac and renal causes: diuretics (furosemide 40 mg) and treat the cause.
• Symptomatic: preservative free lubricating drops every 1 to 2 hours, lubricating ointment at night, cold compresses, head elevation, and a mild topical steroid (prednisolone 0.5 to 1 percent four times daily) for inflammatory chemosis for a short course.
• Hypertonic saline 5 percent drops or ointment to draw out fluid.
• Protect the cornea: taping or temporary tarsorrhaphy if lids cannot close, moisture chamber.
• Refractory localised chemosis (conjunctival lymphangiectasia): conjunctival incision and drainage, or conjunctival excision with cautery, or subconjunctival injection of triamcinolone 40 mg/mL (0.1 to 0.2 mL).
• Review within 24 to 48 hours; urgent referral for orbital signs.