Topographic correlation between multifocal electroretinography, microperimetry, and spectral-domain optical coherence tomography of the macula in patients with birdshot chorioretinopathy

To correlate the findings of retinal function with multifocal electroretinogram (mfERG), microperimetry (MP), and structural assessments with spectral-domain optical coherence tomography (SD-OCT) in topographically corresponding areas of the macula of patients with birdshot chorioretinopathy (BSCR). Patients diagnosed with BSCR by clinical and imaging findings were included in the study. The mfERG was performed using 61 hexagon stimulus patterns grouped into 5 rings (Diagnosys Inc., USA). Individual responses [N1-P1 amplitudes in nanovolt (NV)/degree2 and P1 implicit time in milliseconds (msec)] for each hexagon in the central 3 rings (R1, 0°–2.3°; R2,2.3°–7.7°; and R3, 7.7°–12°) were obtained (19 hexagons). MP examination consisted of Polar 3–12° test with 28 points in 3 concentric rings with diameters of approximately 2.3°, 6.6°, and 11.1° from the foveal center. SD-OCT was performed using macular scans of 20° × 20°. The retinal sensitivity values on MP and thickness values of retinal layers were correlated with the responses on the mfERG for each topographically correlated hexagon. Sixteen eyes of eight patients were included in the study (mean age, 59.87 ± 10.01 years; range, 41–73 years). The amplitudes and the implicit times on mfERG and retinal sensitivities on MP were decreased for each of the 19 hexagons. Considering retinotopically matched points, there was correlation between the retinal sensitivities and mfERG implicit times and response amplitudes in all three rings. The thickness of the retinal pigment epithelium showed modest correlation with the mfERG parameters (ρ = 0.29; p = 0.04). The structural changes on SD-OCT, such as IS-OS disruption, were associated with changes in the mfERG trace arrays. The structural and functional assessments in retinae of eyes with BSCR suggest that each imaging tool may be capturing unique aspects of retinal dysfunction. Multimodal imaging may allow detailed analyses of retinal damage at various corresponding loci. These findings are important when considering the use of these techniques in BSCR.