Electroretinographic monitoring in birdshot chorioretinopathy

PURPOSE: To evaluate electroretinography (ERG) during long,term follow,up in birdshot chorioretinopathy (BCR). DESIGN: Retrospective, comparative interventional case series. METHODS: SETTING: University subspecialty clinic. PATIENT POPULATION: Twenty,three HLA-A29-positive patients with BCR and 40 normal control subjects. INTERVENTION PROCEDURE: Patients were monitored with ERG approximately annually. Treatment was according to best medical judgment. MAIN OUTCOME MEASURES: Baseline ERG values, vision, and ERG values during observed and treated intervals. RESULTS: Median age of patients was 52 years, and 19 patients were untreated at baseline. Eighty,two ERGs were performed. Eighteen patients had more than one ERG; mean follow-up of these patients was 40.2 months +/- 31.2, median 23 months. At baseline, several ERG parameters were statistically reduced compared with control subjects when adjusted for age. The combined rod,cone and cone b/a wave ratios did not differ from control subjects (P = .45 and 0.14). Scotopic rod and combined rod,cone b-wave amplitudes were statistically correlated with baseline vision, as were implicit times for the combined rod-cone a-wave, cone a-wave, and cone flicker b-wave. Median visual acuity was 20/25 and did not change during follow-up. Most ERG parameters showed marked worsening during observed intervals. During treated intervals, the ERG declined at a rate consistent with aging. CONCLUSIONS: Many ERG parameters in patients with BCR greatly differ from control subjects, correlate with vision, and worsen during observation. Selected patients may show improvement in ERG with treatment. The cone b-wave flicker implicit time was most often associated with clinically important measures such as vision, duration of symptoms, and deviation from normalcy.