Oscillatory potentials in patients with birdshot chorioretinopathy

The electroretinogram (ERG) has proven to be useful in the evaluation and monitoring of patients with posterior uveitis. ERG oscillatory potentials (OPs) are sometimes reduced in many uveitic eyes with otherwise grossly normal ERG responses. This study compares ERG parameters, including OPs, between patients with birdshot chorioretinopathy, other posterior uveitis, and controls.

This was a retrospective case-control study. Sixty-four patients seen at a clinical practice had a total of 93 visits during which ERG was performed on both eyes. ERG data from 93 age-matched controls were also collected. Root-mean-squared (RMS) energy of the OPs was calculated using Fourier analysis for 88 patients and 88 age-matched controls for whom complete data were available. Photopic flicker amplitudes, photopic flicker latencies, scotopic b-wave amplitudes, and OP RMS values were compared between patients and controls. Diagnostic performance was assessed using receiver operating characteristic (ROC) curves.

The mean ages of patients and controls were 55.9 ± 10.8 (SD) years and 55.1 ± 11.5, respectively. 83% of the patients had a diagnosis of BCR. The mean OP RMS value was significantly different in patients (15.6 µV ± 9.7 µV) versus control eyes (33.0 µV ± 12.7 µV), p < 0.001. Area under the ROC curves (AUROC) was 0.75 for photopic flicker amplitudes, 0.77 for photopic flicker latencies, 0.72 for scotopic b-wave amplitudes, and 0.88 for OP RMS. AUROC was significantly different between OP RMS and photopic flicker amplitudes (p < 0.001), between OP RMS and flicker latencies (p = 0.0032), and between OP RMS and scotopic b-wave amplitudes (p < 0.0001).

Analysis of OPs shows greater sensitivity and specificity in the diagnosis and evaluation of patients with birdshot chorioretinopathy than photopic and scotopic ERG amplitudes and photopic flicker latencies.