Electroretinogram Changes in the Sound Eye of Subjects with Unilateral Necrotizing Herpetic Retinitis

PURPOSE: To evaluate electroretinogram (ERG) changes in the contralateral normal appearing eye of patients with unilateral acute necrotizing herpetic retinitis (NHR). METHODS: This interventional case series includes subjects with acute unilateral NHR. All patients were treated with intravenous followed by oral acyclovir and systemic steroids. Main outcome measures were changes in a- and b-wave amplitudes of scotopic and photopic full-field ERG in the sound eye, 1 and 3 months after therapy as compared to baseline. Twenty normal subjects served as controls. RESULTS: Forty eyes of 20 patients including 12 male and 8 female subjects with mean age of 44.1±11.5 (range 22 to 66) years were studied. Twenty unaffected eyes were the subject of the current study. The retina in all of these eyes remained intact during the course of the study. In the sound eyes, mean b-wave amplitude of the maximal combined response ERG before initiation of treatment was 229.5±38.8 microvolts which increased to 356.1±34.0 (P<0.001) and 365.8±32.7 (P<0.001) microvolts 1 and 3 months after treatment, respectively. Corresponding figures for b-wave amplitudes of the cone response ERG were 24.9±6.0, 47.0±12.9 (P<0.001) and 52.8±12.7 (P<0.001) microvolts, respectively. Visual acuity of all sound eyes remained unchanged throughout the study. CONCLUSION: Despite normal retinal appearance and intact visual acuity in the sound eyes of patients with NHR, electrophysiological changes were observed. Prompt diagnosis and management of NHR and continuation of medication for 3 months may reverse subclinical ERG changes and reduce the risk of progression to overt clinical disease.