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Jared E Knickelbein, Maggie Wei, Brett G Jeffrey, Robert B Nussenblatt, H Nida Sen; Variability in full-field electoretinogram measurements in patients with birdshot chorioretinopathy. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3310.
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© ARVO (1962-2015); The Authors (2016-present)
Inter-session variability of full-field electroretinogram (ffERG) measurements among people without retinal disease have been reported at >40%. This study aimed to examine the inter-session variability in ffERG measurements in patients with birdshot chorioretinopathy as this test is often used to monitor disease progression.
Retrospective review of eleven patients with clinically quiet birdshot chorioretinopathy (7 women, 4 men, all HLA-A29+) that were evaluated with serial ffERGs. Patients were included if they had more than one ffERG on more than one visit and if they were deemed clinically quiet without escalation of immunosuppressive therapy over the course of these visits. A mean of 6.9 (range 2-13) ffERGs were conducted per patient over a mean of 46.2 months (range 1.4 -112.4). Right and left eyes were evaluated separately. Repeatability coefficients were calculated for each parameter, and Jackknife resampling was used to derive 95% confidence intervals (CIs).
For right eyes, repeatability coefficients were 0.26±0.02 log μV and 0.30±0.03 log μV for scotopic (0 dB flash) a-wave and b-wave amplitudes, respectively, and 0.27±0.03 log μV for photopic 30-Hertz (Hz) flicker amplitudes. For left eyes, reproducibility coefficients were 0.21±0.01 log μV and 0.28±0.03 log μV for scotopic (0 dB flash) a-wave and b-wave amplitudes, respectively, and 0.44±0.09 log μV for photopic 30-Hz flicker amplitudes. These repeatability co-efficients indicate amplitude reductions of 45%, 50%, and 47% in the right eye and 39%, 47%, and 63% in the left eye would be considered significant for scotopic a-wave, scotopic b-wave, and photopic 30-Hz flicker, respectively.
Here we define repeatability co-efficeints for the ERG that set the minimum level for meaningful clinical change in birdshot chororioretinopathy patients. Although variability exists in ffERG measurements in patients with clinically quiet birdshot chorioretinopathy, this variability is similar to previously published variability measurements in normal eyes, as well as those with X-linked retinoschisis, another retinal disorder affecting the inner retina, and retinitis pigmentosa.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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