Purpose Orbital cellulitis is a potentially blinding and life-threatening condition. There are little published data on the incidence of orbital cellulitis and little is known about the differences between children and adults affected. The purpose of this study was to identify the incidence, aetiology, management and outcome of orbital cellulitis in children and adults in Scotland.

Methods This study was a 1-year prospective observational study using the Scottish Ophthalmic Surveillance Unit reporting system among Scottish ophthalmologists.

Results The response rate from ophthalmologists was 66.4%. There were 15 children and 5 adults reported giving an incidence of 1.6 per 100 000 and 0.1 per 100 000 in children and adults, respectively. 47% of children had a preceding upper respiratory tract infection with 87% having radiological evidence of sinus disease. Within the adult group, there was preceding immunosuppression and trauma. Streptococcus (66%) and Haemophilus (46%) species were the most commonly isolated pathogens in children. Respiratory pathogens were less predictable in adults. All patients were treated with intravenous antibiotics. All children with orbital and subperiosteal abscesses had surgery; one adult with orbital abscess did not have surgery. There were two cases of series morbidity: one intracranial spread of infection and one evisceration.

Discussion The incidence of orbital cellulitis is higher in children than in adults. In children, it commonly follows upper respiratory infection and sinus disease; however, in adults, preceding illness and trauma are more common. Respiratory pathogens are common in affected children. Intravenous antibiotics and surgical treatment of abscesses remain the preferred management.