True abscess formation is rare in bacterial orbital cellulitis; consequences for treatment.

BACKGROUND: Pre- or retroseptal bacterial orbital cellulitis (pOC/rOC) is not an uncommon orbital disease. Treatment consists of antibiotics with or without surgical drainage. Several questions regarding course, complications and outcome of treatment are unanswered and the indication for surgery is not well defined. The aim of this study is to: 1. describe the outcome of orbital cellulitis (OC) in a large cohort, 2. assess the significance of Chandler's classification, 3. assess the incidence of abscess formation in OC, and 4. redefine criteria for surgery.

METHODS: Retrospective case series of patients with OC seen between 1-1-2007 and 1-1-2014 in a tertiary referral center.

RESULTS: Sixty-eight patients presented with (presumed) bacterial pOC. Two out of these 68 developed rOC. All 68 patients had a full recovery. Forty-eight patients presented with rOC. Four out of 48 (8%) had intracranial extension of the infection at the time of admission. No admitted patient developed distant seeding. Only four (8%) patients with rOC had a true orbital abscess. In the other 92% we found a diffuse orbital inflammation or a subperiosteal empyema. Forty-four (92%) patients with rOC had a full recovery.

CONCLUSIONS: 1. The prognosis of both pOC and rOC nowadays is generally favorable. 2. Chandler's classification is of little use. 3. True abscess formation in OC is rare. 4. The indication for surgical intervention must be based on the clinical presentation and the assessment of true orbital abscess formation.