Andrew Dorman1,2, Mark Donaldson1,3

Purpose: To determine the utility of aqueous versus vitreous humour polymerase chain reaction based- assays in the diagnosis of Acute Retinal Necrosis. To report the viral aetiology of a cohort of ARN patients.
Method: Retrospective, comparative case series of patients diagnosed with ARN from three major pub- lic ophthalmology clinics from 1997-2017.
Results: Fifty eyes of forty-six patients were diag- nosed with ARN.
Diagnostics PCR testing of ocular humour was per- formed in 86% of eyes (43/50 eyes). Of the eyes which underwent only testing of aqueous humour, a positive PCR was returned in 20/22 tests. Of the eyes which underwent only testing of vitreous humour, a positive PCR was returned in 11/14 tests. Seven eyes underwent testing of both humours, returning positive PCRs for both in 5/7 eyes. One yielded a positive PCR for vitreous but negative result for aqueous humour.
Viral aetiology: Varicella-Zoster and Herpes Simplex Viruses accounted for 58% and 32% of infections, respectively. CMV and EBV were isolated as co- pathogens with VZV in one eye each. Five eyes were diagnosed solely on clinical criteria.
Conclusions: VZV is the most common aetiology of ARN followed by HSV1/2. PCR demonstrated high sensitivity and specificity, and was amenable to small volume samples from ocular humours. Aque- ous PCR was non-inferior to vitreous PCR and therefore should be first-line diagnostic investiga- tion of clinically suspected ARN as it avoids the the- oretical risk of inducing vitreous traction in an eye at high risk of retinal detachment.