OP2.6 | Proptosis: Causes, Differentiation and Management — Summary & Reflection

KEY TAKEAWAYS

Proptosis is forward displacement of the globe and is classified by direction (axial = intraconal, eccentric = extraconal), laterality (unilateral vs bilateral), and time course (acute vs chronic). Thyroid eye disease is the commonest cause of proptosis in adults and the commonest cause of bilateral proptosis. In children, rhabdomyosarcoma is the most dangerous cause and must be biopsied urgently. The Hertel exophthalmometer measures proptosis (normal ≤20 mm; asymmetry >2 mm = significant). Intraconal lesions produce axial proptosis; extraconal lesions produce eccentric proptosis — the direction of eccentric displacement points away from the causative lesion. Pseudoproptosis must always be excluded first. Investigation follows the clinical lead: CT for bony detail and acute trauma, MRI for soft-tissue/optic nerve characterisation, TRAb and TFTs for adults. Management is cause-specific; universal principles are corneal protection (lubricants, moisture chamber) and serial optic nerve monitoring (colour vision). Compressive optic neuropathy — heralded by colour desaturation before acuity loss — is the sight-threatening emergency requiring urgent orbital decompression.

REFLECT

Think about the last clinical encounter (real or simulated) where you saw a patient with an orbital or periorbital abnormality. Looking back with the framework from this module: could you now classify the problem by direction, laterality, and time course? What single additional piece of information (examination finding or investigation) would most change your differential diagnosis? If the patient had been a child rather than an adult, how would your approach have changed, and why? These questions have no single right answer — they are designed to help you practise the systematic clinical reasoning that converts the facts in this module into safe, effective clinical decisions.