Ophthalmology: Proptosis Diagnosis

Study Notes

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.

Description

This quiz covers the diagnosis and features of proptosis, a protrusion of the eye caused by a space-occupying lesion. Learn about exophthalmos, its measurement, and the clues to underlying pathological processes.