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.