Full-field electroretinogram (ERG) has shown promise as an objective visual function test to monitor the progression of birdshot chorioretinopathy (BCR).

Because of the recurrent and progressive nature of BCR — also known as birdshot uveitis  — long-term treatment is required to prevent severe vision loss. Treatments can include systemic corticosteroids or immunomodulatory therapy. However, both are associated with potentially serious side effects, according to research published in the Asia-Pacific Journal of Ophthalmology. ERG testing can help clinicians establish proper regimen and dosing, titrated to the disease activity, can help reduce these risks.

ERG is frequently used to monitor BCR. Abnormalities captured via ERG have been associated with recurrence of inflammation, and treatment of BCR can result in improved ERG results, sometimes sooner than clinical signs of recovery are evident, according to the investigators.


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In this retrospective cross-sectional study, researchers reviewed 21 eyes of 11 patients with BCR with prior ERG and Goldmann kinetic perimetry. They used a generalized estimating equation for statistical analysis, and isopters V4e and I4e were modeled as separate outcomes with each parameter of ERG as the main independent variable. The main outcome measured was the presence or absence of correlation between the Goldmann isopters and ERG parameters, including the amplitudes and implicit times of dark-adapted (DA) and light-adapted (LA) a-waves and b-waves (DA 0.01, DA 3.0, DA 10.0, and LA 3.0) and LA 30 Hz.

The team found a strong positive correlation between the size of isopter V4e and all the scotopic and photopic standard ERG amplitudes [P <.0001 for all, except LA 3.0 a-wave (P =.0019) and LA 30 Hz (P =.0026)]. For the implicit times, only DA 3.0 a-wave (P =.007) and LA 30 Hz (P <.0001) showed significant negative correlations. There were no correlations between the size of isopter I4e and any ERG amplitudes, according to the researchers. However, 3 implicit times showed some negative correlation: DA 3.0 a-wave (P <.0001), DA 10.0 b-wave (P =.0251), and LA 3.0 b-wave (P <.0001).

The retrospective nature of the study and its small sample size are its main limitations. Additionally, this study examined patients at various stages of disease severity. Further, the photopic negative response was not analyzed, so the functional status and degree of inner retina involvement—and its correlation with VF in BCR—is not known.

Disclosure: One of the study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.  

Reference

Ameri H, Naser M, Choudhury F, et al. Electroretinogram and visual field correlation in birdshot chorioretinopathy. Asia Pac J Ophthalmol. 2021;10(2):208-211. doi:10.1097/APO.0000000000000374