To analyse the prognostic factors for visual acuity in acute retinal necrosis (ARN) patients treated non-surgically. The clinical data of ARN patients who visited our hospital from January 2010 to January 2023 were retrospectively analysed. Twenty-four patients (29 eyes) were included. Aqueous humour samples were collected from 20 out of 29 eyes, and PCR confirmed that 85% (17/20) of the eyes had VZV infection, 10% (2/20) had CMV infection, and 5% (1/20) had HSV infection. All patients were treated with intravenous antiviral agents. Intravitreal ganciclovir and oral corticosteroids were given according to the patients' wishes. A comparison of visual acuity at the time of first identification of inactive ARN with that at the first visit revealed that 16 (55.2%) eyes improved and 13 (44.8%) did not improve. Logistic regression analysis revealed that risk factors for failure to improve vision after treatment included retinal detachment (odds ratio [OR],33.75; 95% CI, 3.245-351.067; P = 0.003), necrotising retinitis involving the posterior pole (odds ratio [OR],8.167; 95% CI, 1.297-51.403, P = 0.025), and arteritis involving the large retinal arteries (odds ratio [OR],9.167; 95% CI, 1.493-56.297; P = 0.017). The VZV viral load in the aqueous humour at initial presentation was significantly associated with visual prognosis (r = 0.688, P = 0.013), retinal detachment (τ = 0.597, P = 0.021) and the extent of retinal necrosis (τ = 0.57, P = 0.027). The neutrophil to lymphocyte ratio (NLR) of VZV-infected patients at first presentation was significantly correlated with the prognosis of visual acuity (r = 0.616, P = 0.033) and retinal detachment (τ = 0.728, P = 0.004). High NLR and viral DNA copy number in the aqueous humour at the initial presentation, as well as subsequent retinal detachment, necrotising retinitis involving the posterior pole, and arteritis involving the large retinal arteries were risk factors for poor visual prognosis in VZV-infected ARN patients.