Acute retinal necrosis: a national population-based study to assess the incidence, methods of diagnosis, treatment strategies and outcomes in the UK.

AIM To determine the incidence, methods of diagnosis, treatment strategies and outcomes for acute retinal necrosis (ARN) in the UK. METHODS A 12-month active case ascertainment study was carried out between March 2001 and March 2002 to record cases of ARN presenting to ophthalmologists via the British Ophthalmological Surveillance Unit (BOSU) reporting system. Questionnaires were sent to the reporting consultants, requesting data on patient characteristics, presentation, clinical findings, investigations and treatment. Diagnosis was made using the American Uveitis Society diagnostic criteria. Further questionnaires were sent at 2 weeks and 6 months to assess outcome and therapies. RESULTS 74 cases of ARN were reported by 58 consultants between March 2001 and March 2002. Questionnaires were returned for 49 cases (66.2%), of which 18 (36.7%) were excluded. Of the 31 cases included, 22 (71.0%) were male and 9 (29.0%) were female. The age range was 13 to 85 years (mean 54.3 years). 28 cases (90.3%) were unilateral, with 3 patients (9.7%) presenting with bilateral ARN. An aqueous or vitreous biopsy was performed in only 18 patients, with one patient having both. Herpes viral DNA analysis was performed on all 19 biopsies, with identification of the viral DNA in 16; results from 3 biopsies were not documented. Varicella zoster virus (VZV) was the commonest cause identified in 10 patients (56%). Of the 31 subjects, 27 (87.1%) were treated for ARN with systemic antiviral treatment: with intravenous antiviral in 23 cases (85.2%) and oral antiviral in 4 cases (14.8%). 21 of these patients went on to receive oral antiviral maintenance therapy. In addition to antiviral treatment, systemic steroids were given to 16 subjects (51.6%). Surgical intervention for retinal detachment was performed on 5 patients. CONCLUSIONS During the 12-month study period, 31 cases of ARN met the diagnostic criteria set by the American Uveitis Society. The incidence in the UK based on this study is approximately 1 case per 1.6 to 2.0 million population per year. We have ascertained that the management of ARN throughout the UK is variable, suggesting that national guidelines would be of benefit.