Further studies employed cross-sectional imaging by optical coherence tomography (OCT) or optical coherence tomography angiography (OCTA) (Parisi et al., 2001; Kromer et al., 2014; Cunha et al., 2016; Ferrari et al., 2017; Polans et al., 2017; Polo et al., 2017; Bulut et al., 2018; Janez-Escalada et al., 2019; Salobrar-Garcia et al., 2019), which revealed structural abnormalities and cell neurodegeneration in the retina.