[Anatomic-functional correlations in birdshot chorioretinopathy: An observational single-center prospective study]

The purpose of this study was to identify anatomic-functional correlations in patients with Birdshot chorioretinopathy in order to better understand the mechanisms of visual loss.

We conducted a single-center observational prospective study at the Nantes University Medical Center including all patients followed for Birdshot chorioretinopathy between January 2019 and July 2019. The parameters studied were visual acuity, microperimetry, standard automated perimetry, SD-OCT, EDI-OCT, OCT-A, RNFL-OCT, wide-field fundus photographs, and fluorescein and ICG angiography.

Forty-four eyes were studied. A significant correlation was found between visual acuity and retinal thickness (P=0.002, r=0.44), but not choroidal thickness (P=0.16). A significant correlation was also observed between retinal sensitivity and total macular thickness (P<0.001, r=0.68) as well as inner retinal thickness (P<0.001, r=0.65), while the correlation was weaker with choroidal thickness (P=0.03, r=0.32). There was a weak correlation between retinal sensitivity and superficial capillary density (P=0.02, r=0.42) as well as deep capillary density (P=0.02, r=0.41). The peripheral hypo-autofluorescent zones correspond to the visual field defects, but these defects are larger than the hypo-autofluorescent zones. Patients with paracentral or peripheral field defects had a history of vasculitis more often than hypo-ICG spots.

We found significant correlations between functional parameters such as visual acuity and retinal sensitivity and retinal anatomic parameters, particularly the inner retina, while there was no correlation shown with choroidal anatomic parameters.

The main results of our study suggest a retinal rather than choroidal origin of the degradation of visual function in birdshot chorioretinopathy.