Abstract
PurposeTo 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).MethodsPatients 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.ResultsSixteen 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.ConclusionsThe 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.
Highlights
Since its first description in 1980 [1], birdshot chorioretinopathy (BSCR) remains a management challenge due to its chronic progressive nature resulting in significant chorioretinal damage
All the participants included in the study had reliable MP imaging and adequate quality spectral-domain optical coherence tomography (SD-OCT) and multifocal electroretinogram (mfERG) scans
Mean values of full retinal thickness (FRT) and retinal pigment epithelium (RPE) thickness, when compared with the retinal sensitivities at the MP test points, showed no significant correlation. This correlation between layer thickness and retinal sensitivity indicates that retinal thickness did not affect the sensitivity at/ around the lesion area – contrary to the results reported previously in uveitis subjects [16]
Summary
Since its first description in 1980 [1], birdshot chorioretinopathy (BSCR) remains a management challenge due to its chronic progressive nature resulting in significant chorioretinal damage. The disease course may appear to be clinically stable as the Snellen’s visual acuity may not worsen. This led clinicians to believe that BSCR represents an inflammatory uveitic entity with a selflimiting, benign course [2, 3]. Serial assessment of patients with BSCR using electroretinograms [5, 6] and visual field testing [7] has demonstrated a chronic, relentless course of the disease even in the absence of clinically detectable intraocular inflammation [8]. Studies using noninvasive imaging techniques such as spectral-domain optical coherence tomography (SD-OCT) have shown significant atrophy of the retinal layers of the macula and mid-periphery among patients with BSCR [9, 10]. The preferred longterm follow-up approach of patients with BSCR consists of multimodal imaging with an aim to detect and treat early signs of pathological damage [12]
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