Purpose: Pericentral visual field changes and disruption of the ellipsoid layer on spectral domain optical coherence tomography (SD-OCT) are the main features of antimalarial retinal toxicity. C-Scan OCT or "en face" enables a topographic frontal view of the changes observed within the different retinal layers in particular the ellipsoid layer. The aim of this prospective study was to compare multifocal ERG (mfERG) responses with the results of C-Scan OCT ("en face" OCT) in patients with abnormal visual field and to analyze relationships between the structural and functional abnormalities.
Methods: In 354 consecutive patients screened for antimalarial toxicity between January 1, 2014 and December 31, 2016, central visual field, mfERG recording, C-Scan OCT and short-wavelength fundus autofluorescent imaging were performed.
Results: Among the 17/354 patients with abnormal central visual field results, all presented with abnormalities on the mfERG at least in one eye. In 16/33 eyes, there was a good concordance between focal loss of the mfERG response and the disruption of the ellipsoid layer on C-Scan OCT. In one eye with characteristic changes in the ellipsoid layer on the C-Scan OCT, the mfERG was normal, whereas in three eyes the mfERG was abnormal in eyes with a normal C-Scan OCT.
Conclusions: The contribution of the C-Scan OCT changes remains difficult to establish as there is no strict concordance with the local ERG responses. Although C-Scan OCT technology provides a new approach in analyzing focal abnormalities in the photoreceptor-retinal pigment epithelium interface, the sensitivity of this method compared with mfERG and other tests (central visual field, B-Scan OCT) needs to be evaluated. This study is still ongoing on a larger cohort.
Keywords: En face OCT; Hydroxychloroquine retinopathy; Multifocal electroretinogram; Optical coherence tomography; Ring ratio.