Ophthalmology: Proptosis Diagnosis

Proptosis (Exophthalmos)

• Proptosis is a protrusion of the eye caused by a space-occupying lesion.
• It can be measured with an exophthalmometer.
• A difference of prominence of more than 3 mm between the two eyes is significant.
• The direction of displacement of the eye can suggest the location of the lesion:
  • Directly forward: intra-conal lesion (e.g. optic nerve sheath meningioma)
  • To one side: extra-conal lesion (e.g. tumour of the lacrimal gland)
• Transient proptosis induced by increasing cephalic venous pressure (Valsalva manoeuvre) is a sign of orbital varices.
• The speed of onset of proptosis can suggest the aetiology:
  • Slow onset: benign tumour
  • Rapid onset: inflammatory disorders, malignant tumours, and caroticocavernous fistula
• Presence of pain may suggest infection (e.g. orbital cellulitis).

Enophthalmos

• Enophthalmos is a backward displacement of the globe.
• It is a feature of an orbital 'blowout fracture', when blunt injury to the globe and orbit fractures a thin orbital wall and displaces orbital contents into an adjacent sinus.
• It is also seen in Horner's syndrome, but this is a pseudo-enophthalmos due to narrowing of the palpebral fissure.

Infective Disorders

• Orbital cellulitis is a serious condition that can cause blindness and may spread to cause a brain abscess.
• Infection often arises from an adjacent ethmoid sinus.
• Common causative organisms are Staphylococcus and Streptococcus.
• Patient presents with:
  • Painful, proptosed eye
  • Conjunctival injection
  • Periorbital inflammation and swelling
  • Reduced eye movements
  • Possible visual loss
  • Systemic illness and pyrexia
• MRI or CT scan is helpful in diagnosis and planning treatment.
• Treatment usually involves intravenous broad-spectrum antibiotics, but may require draining an abscess or decompressing the orbit.
• Optic nerve function must be closely monitored.

Orbital Tumours

• Various tumours can produce signs of orbital disease, including:
  • Lacrimal gland tumours
  • Optic nerve gliomas
  • Meningiomas
  • Lymphomas
  • Rhabdomyosarcomas
  • Metastasis from other systemic cancers
• CT or MRI scan will help with diagnosis.
• Systemic investigation may be required to determine the site of a primary tumour.
• Malignant lacrimal gland tumours carry a poor prognosis.
• Benign tumours still require complete excision to prevent malignant transformation.
• Optic nerve gliomas may be associated with neurofibromatosis.